Highways Agency

Incident on 28 February 2001 at Little Heck Railway Bridge, Issued August 2002

Highways Report, 30 March 2001

Report by:

Investigations & Risk Management Group
Transport Research Laboratory
Old Wokingham Road
Crowthorne
Berkshire
RG45 6AU

Tel: 01344 770892
Fax: 01344 770894
DX: 48602 Crowthorne

Document Ref: 03719/106/2

EXECUTIVE SUMMARY

GLOSSARY OF MAIN TERMS

APPENDIX A - Tables Of Data From HARRIS Site Survey

DRAWINGS

PHOTOGRAPHS

Executive Summary

The Transport Research Laboratory (TRL Limited) has been appointed by the Highways Agency to undertake detailed independent investigations into the pertinent highways aspects of an incident that occurred during the morning of 28 February 2001 at Little Heck Railway Bridge, between Junctions 34 and 35 of the M62 Motorway.

The incident involved a Land Rover County motor vehicle towing a double axle trailer unit transporting a Renault Savanna motor car. This vehicle combination left the westbound carriageway of the motorway before reaching the bridge. It then descended the embankment to the nearside of the carriageway, breached two wooden boundary fences and came to rest immediately adjacent to, or partially across, the up-line of the East Coast main railway line. The Land Rover was then hit by a high-speed passenger train, which was consequently de-railed and eventually struck by a goods train some distance to the south of the motorway, near the village of Great Heck. As a result of the incident, ten people tragically lost their lives.

Investigations conducted by the Health and Safety Executive (HSE), the railway industry, Humberside Police, North Yorkshire Police and British Transport Police are continuing at the time of writing of this report.

TRL's investigation has involved the detailed examination of the scene of the accident; specialist surveys of skidding resistance and other road surface characteristics, as well as consideration of documentation relating to the design, construction and maintenance of the relevant section of the M62 Motorway. TRL staff were on site between 28 February and 5 March 2001 inclusive.

TRL issued a Preliminary Opinion Report into the incident on 6 March 2001 and, since then, the data and other information obtained has been analysed and studied in detail so as to prepare this full investigation report. All of the opinions and conclusions expressed in the Preliminary Opinion Report have been supported by the further investigations and, in terms of the incident as a whole, the following conclusions have been drawn:

The carriageway provision and geometry at the material location are consistent with motorway provision generally throughout the UK and provide no cause for concern.
The material section of the M62 Motorway has been maintained in a responsible manner in general accordance with the required standards.
It appears that, at the time of Mr Hart's accident, the carriageway surface was in a good condition and met the required standard of skidding resistance.
There is currently no indication that any debris or defect was present on the carriageway surface around the material time and location.
Although the vicinity was subject to a prolonged period of cold weather around the time of the accident, the available evidence does not indicate that frost, ice or snow was present on the road surface around the time of Mr Hart's accident.
The timing and extent of winter maintenance operations undertaken around the time of the material accident are considered to have constituted a reasonable response to both the weather forecast information received and the actual weather conditions experienced.
The nearside front wheel of the Land Rover appears to have first mounted the verge approximately 50 metres in advance of the safety fence installed on the nearside verge of the westbound carriageway in advance of the Little Heck Bridge parapet, and the safety fence was not struck during the course of the incident.
This safety fence is 42.7 metres long in total, of which 33.5 metres constitutes full height provision and the remaining 9.2 metres comprising ramp down to a concrete terminal. The safety fence type and length complies with all relevant historical and current standards.
In order for the full width of the front of the Land Rover to have struck a section of full height safety fence, the safety fence would have needed to extend along the verge for more than twice its current length.
The Land Rover and its loaded trailer are greater in both mass and dimension than the vehicle configurations to which normal in-service safety fences are designed and tested. Therefore, it is extremely difficult to assess whether the safety fence provided at the material location would have contained the vehicle combination, even if it had been struck during the course of the incident. However, it is considered likely that some containment would have occurred and that this probably would have prevented the material vehicle combination from reaching the railway line.
The accident history of the material site has been analysed. In the six years up to the 31 December 2000, no Personal Injury Accidents are reported to have occurred on the westbound carriageway of the M62 Motorway within one kilometre in advance of, and including, the Little Heck Railway Bridge.

TRL Limited, 30 March 2001

Introduction

1.1 The Transport Research Laboratory (TRL Limited) has been appointed by the Highways Agency to undertake detailed independent investigations into the pertinent highways aspects of an incident that occurred during the morning of 28 February 2001 at Little Heck Railway Bridge, between Junctions 34 and 35 of the M62 Motorway.

1.2 A TRL Preliminary Opinion Report into the incident was issued on 6 March 2001 and this Highways Report is intended as a full and detailed investigation report.

Brief Summary of Incident

1.3 The incident involved a vehicle leaving the westbound carriageway of the M62 Motorway prior to reaching the Little Heck Railway Bridge. The vehicle traversed the nearside verge at a relatively shallow angle, descended the slope of the embankment, traversed further along the base of the embankment, damaged two boundary fences between the highway and adjacent land, descended into the railway cutting and eventually came to rest immediately adjacent to, or partially across, the up-line, i.e. the southbound track, of the main East Coast railway.

1.4 Subsequently, this vehicle was struck by a high speed passenger train, travelling between Newcastle and London, which was consequently de-railed and eventually struck by a goods train travelling in the opposite direction, near the village of Great Heck. As a result of the overall incident, ten people tragically lost their lives.

Other Investigations

1.5 The Health and Safety Executive (HSE) is conducting its own investigation into the railway aspects of the collision. The rail industry is also conducting detailed investigations, as are Humberside Police, North Yorkshire Police and British Transport Police. These investigations are all ongoing at the time of writing.

Highway Responsibilities

1.6 The Highways Agency (HA) is the executive agency of the Department of Environment, Transport and the Regions (DETR) responsible for the maintenance and upkeep of the English Trunk Road and Motorway network.

1.7 The HA has a number of regional offices throughout the country, each of which co-ordinate the management and maintenance of the motorway and trunk road network in their region. The HA regional office responsible for co-ordinating the management and maintenance of the relevant section of the M62 Motorway is in Leeds.

1.8 The HA contract out the management of motorway and trunk road maintenance operations to third parties, referred to as Maintaining Agents (MAs). The MA for the material section of the M62 Motorway is WSP Civils Ltd (WSP).

1.9 The maintenance operations themselves are contracted out by HA to a Term Maintenance Contractor (TMC). The TMC for the relevant section of the M62 Motorway is Carillion Highway Maintenance Limited (Carillion).

1.10 Therefore, HA Leeds Office co-ordinates the management and maintenance of the material section of motorway, and WSP manages the maintenance operations, which are undertaken by Carillion.

1.11 The HA is investigating highway related aspects of the incident on behalf of the DETR and TRL's independent investigation has been undertaken to assist in this process.

Scope of TRL Investigation

1.12 This Highways Report is intended to provide independent comment and opinion on the adequacy and condition of all relevant aspects of the highway at the material location, in comparison with those suggested by national best practice and required by national standards.

1.13 Due to the fact that the Police investigations are still ongoing, little is currently known as to the primary causes of this incident. Therefore, the scope of this report is required to be relatively wide reaching.

1.14 The main issues addressed in this report are as follows:

composition and condition of the road surfacing;
routine highway maintenance operations;
highway winter maintenance operations;
the provision of vehicle restraint systems to the nearside of the westbound carriageway.

Methodology of Investigation

1.15 A six strong TRL investigation team arrived on site at approximately 1430hrs on Wednesday 28 February 2001. The team included highly experienced specialists in the fields of highway design and maintenance. In particular, this included safety fence and highway winter maintenance expertise. Other members of the team specialise in the acquisition of incident data using state-of-the-art 3-Dimensional laser scanning technology and this equipment was used to obtain detailed information concerning the accident scene.

1.16 Whilst on site, the investigation team liaised with staff from HA Leeds, WSP and Carillion. At that time, schedules of relevant documents were requested to be secured and copies of these documents have been provided to the investigators.

1.17 The site was subject to detailed examination, measurements were taken and specialist surveys of skidding resistance and other road surface characteristics were commissioned and then undertaken during the period up to 5 March 2001.

1.18 Since this date, the data obtained from site and all of the relevant documentation has been analysed and considered in detail in order for conclusions to be drawn and opinions expressed within this report.

Circumstances of the accident

2.1 It currently appears that, during the early morning of Wednesday 28 February 2001, Mr Gary Hart was driving a Land Rover County motor vehicle, which was towing a double axle trailer unit loaded with a Renault Savanna estate car, westbound on the M62 Motorway.

2.2 At around 0612 hrs Greenwich Mean Time (GMT) and at a point prior to reaching the Little Heck Railway Bridge, Mr Hart's vehicle and loaded trailer left the carriageway to the nearside. The cause of the vehicle combination leaving the carriageway is currently unknown to the authors of this report.

2.3 Sunrise at that site on the morning of 28 February 2001 was at 0655 GMT. Therefore, it was dark at the time of the accident.

2.4 The first point of contact between the Land Rover and the kerb on the nearside edge of the westbound carriageway has been identified as being 50.2 metres from the safety fence terminal, i.e. 50.2 metres before reaching the safety fence which is situated on the nearside verge in advance of Little Heck Bridge.

2.5 This point of contact is assumed to be have been made by the nearside front wheel of the Land Rover.

2.6 The vehicle proceeded at a shallow angle to the kerb before a second impact point was made at 23.9 metres from the safety fence terminal. This point of contact is assumed to be that of the offside front wheel of the Land Rover.

2.7 From each point of contact, rolling wheel tracks across the verge identify the subsequent course of travel.

2.8 The initial angle of the wheel tracks is between 5 and 6 degrees to the normal direction of travel along the motorway.

2.9 It is evident from the tracks that the vehicle combination continued to leave the motorway, with the offside front wheel missing the end of the safety fence terminal by approximately 7 metres (measured parallel to the carriageway edge), before it travelled down the embankment, which is approximately 3.5 metres high at this point.

2.10 The vehicle combination broke through the wooden post and rail boundary fence between the highway and adjacent private land at the base of the motorway embankment around 16.9 metres before the intersection of that fence with the similarly constructed boundary fence of the railway.

2.11 The vehicle combination continued through the boundary fence of the railway, dropped down into the railway cutting and finally came to rest fouling the East Coast Main railway line (ECML).

2.12 In all, the vehicle combination travelled approximately 100 metres between leaving the carriageway and coming to rest on the railway.

2.13 The Land Rover came to rest either immediately adjacent to, or partly within the up-line, i.e. southbound, track. It appears that, by this time, the trailer had become detached from the Land Rover and had come to rest up against the side of the Land Rover.

2.14 The precise positions of the Land Rover, trailer and Renault Savanna before the train strike is currently unknown to the authors of this report and is subject to investigation by the Police.

2.15 No other road vehicles appear to have been involved in the material accident and the only highway structures impacted were the two wooden boundary fences running perpendicular to each other at the bottom of the embankment between the highway and adjacent land.

2.16 Mr Hart survived the incident and telephoned the emergency services at approximately 0614 GMT. The impact between the high speed passenger train and the Land Rover occurred around this time.

2.17 Drawing No. 03719/106/2/001 comprises a plan showing the path of the vehicle combination in relation to pertinent features of the highway. Drawing Nos. 03719/106/2/002 and 003 provide cross sectional details through sections A-A and B-B respectively, as indicated on the plan. Drawing No. 03719/106/2/004 is a schematic drawing showing the southern side elevation of Little Heck Bridge. These drawings are included to the rear of this report.

2.18 Photographs 1 to 4, also to the rear of this report, show the general area of nearside verge, embankment and railway where the vehicle combination travelled and came to rest.

2.19 It should be noted that the vehicle rest positions shown in the drawings and photographs are the final rest positions following the impact with the train.

Layout and history of the pertinent section of motorway

3.1 It is understood that the material section of the M62 Motorway was constructed in 1974 to technical standards published by the then Department of Transport (now DETR).

3.2 The westbound section of the M62 Motorway between Junction 35 (Langham) and Junction 34 (Whitley Bridge) is generally straight in its alignment and consists of three running lanes and a hard shoulder. As in normal circumstances, broken white line markings and reflecting road studs are used to delineate the running lanes of the carriageway.

3.3 On the approach to the incident scene, the edges of the westbound running carriageway are delineated by continuous white line markings, with the nearside edge line consisting of vibra-line (known colloquially as "rumble-strip"), which is designed to provide audible warning to road users that their vehicle is leaving the running carriageway and entering the hard shoulder. This vibra-line is discussed in greater detail in Chapter 6 of this report.

3.4 The nearside edge of the hard shoulder exhibits a continuous kerb, which is approximately 75 millimetres high. The verge is grassed over.

3.5 On the approach to Little Heck Railway Bridge, the westbound carriageway exhibits a gradual incline and the crossfall, i.e. the transverse slope, is toward the nearside.

3.6 The bridge has the express purpose of carrying the M62 Motorway over the East Coast Main Line railway.

3.7 A continuous double-sided safety fence is provided in the central reserve of the motorway, in order to physically prevent errant vehicles from crossing from one carriageway to the other.

3.8 A length of safety fence is provided on the nearside verge, in advance of, and connected to, the parapet of Little Heck Railway Bridge. This length of safety fence is discussed in detail in the following section and Chapter 9 of this report.

3.9 It is understood that the current surfacing of the M62 Motorway in the vicinity of the material location, was laid in 1993 (westbound carriageway) and 1995 (eastbound carriageway).

3.10 The 1993 resurfacing operation on the westbound carriageway was undertaken as part of major maintenance works undertaken on a length of approximately 7.2 kilometres of this carriageway between Marker Posts 141/8 and 149/0 (with Little Heck Bridge being located near Marker Post 146/1).

3.11 The contract for the works was let by Humberside County Council (then the Maintaining Agent for this section of the M62 Motorway) and was won by Tilcon Construction Limited. It appears that the surfacing at the material location, i.e. in the general vicinity of Little Heck Bridge, was laid between 1 and 5 November 1993, utilising a 40 mm thick wearing course layer of hot rolled asphalt with embedded 20 mm pre-coated chippings.

3.12 The specification for the surfacing is consistent with Highways Agency standards for such applications and the results of post-lay performance/quality control tests indicate that the newly laid surface met the relevant standards for such criteria as surface regularity, which is effectively a measure of anticipated ride quality, and texture depth.

3.13 It appears that a short section of the inside running lane (Lane 1) of the westbound carriageway as it crosses the deck of Little Heck Bridge was re-surfaced again in April 1998. It is understood that this work was undertaken as a result of, and to rectify, the presence of wheel track rutting. Mr Hart's vehicle left the carriageway before reaching the bridge and this section of re-surfacing.

Layout and History of Little Heck Bridge and the Safety Fence

3.14 Little Heck Railway Bridge is a single span, simply supported, reinforced and prestressed concrete structure which carries the M62 Motorway over the East Coast Main railway Line (ECML).

3.15 The bridge is at a skew angle of 11°54'45'' to the motorway, and has a skew span of 19.14 metres. The overall width of the bridge between parapet faces is 33.9 metres, measured square to the deck fascia, with overall carriageway widths of 11.0 metres.

3.16 The designs for the Little Heck Railway Bridge were formulated between October 1971 and June 1972 by the North Eastern Road Construction Unit (NERCU) and the bridge was constructed and commissioned in 1974 upon the opening of the Whitley Bridge to Pollington section of the M62 Motorway.

3.17 On each side of the bridge is a normal containment parapet, given the designation P5. This parapet type has been tested, in controlled test conditions, with a 1500 kg vehicle, impacting the parapet at 110 km/h at an angle of 20°.

3.18 Each parapet is a two rail steel system, mounted on top of reinforced concrete walls. Solid aluminium infill plates were attached to the parapets over the full width of the railway as a part of the later electrification of the railway line.

3.19 The approaches to the bridge are protected by lengths of untensioned, single sided, open box beam (OBB) safety fence, joined to the ends of the parapets using appropriate connection pieces. The safety fence immediately to the east of the bridge on the westbound carriageway exhibits full height for 33.5 metres in advance of the parapet, plus an additional 9.2 metres of ramp down to a concrete terminal. This provides a total length of 42.7 metres. The set-back distances of the safety fence (i.e. the distance between the traffic face of the OBB and the edge of the carriageway) are shown on Drawing No. 03719/106/2/001, to the rear of this report.

3.20 As-built drawings prepared after construction in 1974 show that the parapet was initially protected at both ends by an OBB safety fence, as it is now. However, it appears that the configuration of the fencing may have been altered since the opening of the bridge in 1974.

3.21 This conclusion has been reached due to the as-built drawings (1974) showing the safety fence to be constructed in a straight line, which is not consistent with the set-back flare of the safety fence currently visible today. There is also a mass of concrete in the soil beneath one part of the existing safety fence, which would be consistent with the spacing and location of the supporting posts for, at least that part of the fence, having been altered.

3.22 It is considered likely that the realignment of the safety fence took place during the major maintenance work undertaken on that section of the westbound carriageway in 1993. This is due to the as-built drawings (1974) showing no flare at the ramped down end of the safety fence, but this flare being present both on the 1993 maintenance drawings, and at the time of writing this report.

3.23 In August 1985, British Rail wrote to the then Department of the Environment and Transport seeking approval to improve the parapets of Little Heck Bridge prior to their electrification of the East Coast Main Line. The improvement was required in order for the parapets to continue to comply with standards, as Technical Memorandum BE 5 (1992) Clause 205 (c), states:

"On bridges over railways with existing or programmed overhead electrification, parapets consisting of a plinth surmounted by metal posts and horizontal rails [as at the material location] shall be provided with solid or infill panels immediately above the top of the plinth up to the full height of the parapet."

3.24 (Nb. the nature and status of BE 5 is discussed in detail in Chapter 9 of this report).

3.25 As a result of this communication and the planned electrification, solid aluminium cladding panels were fitted to the parapets in May 1987 by Lindley Fabricators Limited. The main line was then electrified in June 1989.

Trunk road maintenance standards

4.1 Highways Agency policies and standards for trunk road maintenance are contained within the Trunk Road Maintenance Manual (TRMM).

4.2 Volume 2 of TRMM discusses the Highways Agency's requirements for the routine and winter maintenance of motorways and other trunk roads in England. The version of Volume 2 in effect at the present time, i.e. in effect at the time of the incident under investigation, was first issued in February 1996 and has been subsequently amended with Amendment Sets 1 and 2.

4.3 Volume 2 is sub-divided into:

Part 1 - Routine maintenance of highways
Part 2 - Routine maintenance of structures
Part 3 - Winter maintenance

4.4 Part 1 of Volume 2 describes the procedures for, and frequency of, routine highway inspections, which are designed to identify hazardous and other defects, to determine requirements for routine maintenance works and, in some instances, the manner in which maintenance works are to be performed.

4.5 As its title suggests, this Part specifically concerns areas of activity that are generally short term or cyclic, required to keep the highway in good order. It does not deal with longer-term replacement or renewal of the various parts of the highway, although it is recognised that the routine inspection system can play an important role in identifying features that may require eventual replacement or renewal.

4.6 Management procedures for the routine maintenance of highways are implemented by the Routine Maintenance Management System (RMMS), which allows all inspections and other reports, complaints and third party claims to be assessed in conjunction with the established highway inventory, previous maintenance actions and other relevant data.

Routine Highway Inspections

4.7 The Trunk Road Maintenance Manual (TRMM) specifies three types of routine highway inspection:

Safety Inspections - which are designed to identify defects likely to create a danger to the public and therefore require immediate or urgent attention. Such inspections are typically undertaken from a slow moving, double manned vehicle, with the occasional need to proceed on foot. The TRMM states that additional Safety Inspections may be required in response to reports or complaints from the Police, the general public etc. or in response to extreme adverse weather conditions;
Detailed Inspections - which are designed primarily to establish programmes of routine maintenance tasks not requiring urgent execution and are typically undertaken on foot at less frequent intervals than Safety Inspections;
Safety Patrols - these are required to supplement Safety Inspections on the higher priority motorways and trunk roads, in order to provide a more frequent surveillance of the road network to identify serious defects. Safety Patrols are typically required to be undertaken in a single manned vehicle, and at speeds as slow as the general traffic conditions allow.

4.8 The M62 Motorway is categorised as Inspection Category A, which requires it to be subject to weekly Safety Inspections and daily Safety Patrols between Safety Inspections.

4.9 The frequency of Detailed Inspections varies according to the inventory items being inspected. Further information relating to the Detailed Inspection of various highway components is discussed later in this section of the report.

4.10 Detailed Inspections are predominantly undertaken from the hard shoulder, the nearside grass verge or from the nearside lane. However, every two years a Detailed Inspection is required from the central reserve with the offside running lane being coned off to enable this to take place. Inspections undertaken from the central reserve are specifically designed to inspect items within, and adjacent to, the central reserve.

4.11 The TRMM categorises defects identified during Safety Inspections, Detailed Inspections and Safety Patrols into two categories:

Category 1 - requiring prompt attention, as the defect presents an immediate or imminent hazard to road users. Category 1 defects are required to be corrected or made safe at the time of the inspection, if possible. Where this is not possible, temporary or permanent repairs must be completed within 24 hours of detection and, where temporary repairs are adopted, permanent repairs must be undertaken within 28 days;
Category 2 - all other defects. Category 2 defects are further divided into 3 levels and are described (along with Category 1 defects) within the Routine Maintenance Management System (RMMS) Manual.

4.12 In addition to information from routine visual inspections of the highway, engineers may also receive information concerning the condition of the highway network from third parties, such as the general public, the Police and other emergency services.

4.13 The TRMM (Volume 2, Part 1, February 1996) states that motorway carriageways should be subject to Detailed Inspection for minor carriageway repairs (i.e. those not requiring large scale work to strengthen the carriageway or work that would be regarded as structural maintenance) on an annual basis.

4.14 It goes on to state (Chapter 1.13) that motorway safety fences and barriers should be subject to Detailed Inspection every two years.

4.15 Maintenance of safety fences and barriers is generally confined to the repair of damaged sections and ensuring correct assembly and operation. The TRMM states that the repair of damaged sections of safety fence or barrier will usually be instigated by Safety Inspections or reports from other sources and require prompt attention, as they are likely to pose an increased risk to road users. For this reason, the TRMM states that routine maintenance requirements for safety fences and barriers are more onerous than for the majority of other highway features.

4.16 With respect to steel safety fences, such as present at the material location, the TRMM states that mounting height, surface protective treatment and structural condition are required to be subject to Detailed Inspection every two years, in order to detect routine maintenance activities that may be required.

4.17 The TRMM also provides guidance on the Detailed Inspection and maintenance of fences, walls, screens and environmental barriers. With respect to integrity and stock proofing, the TRMM states that boundary fences should be inspected every six months. The timber sections of boundary fences should be subject to Detailed Inspection every five years during the first ten years of its life, and thereafter every two years.

Routine Maintenance of Highway Structures

4.18 Guidance regarding the inspection and routine maintenance of structures is contained within Volumes 1 and 2 of the TRMM and Volume 3 of the Highways Agency's Design Manual for Roads and Bridges (DMRB).

4.19 Section 1 of DMRB Volume 3 contains technical standard BD 63/94 (Inspection of Highway Structures, October 1994) and advice note BA 63/94 (also entitled Inspection of Highway Structures, October 1994), which specify the requirements for inspections of structures.

4.20 BD 63/94 is a technical standard that outlines the various types of inspection required on highway structures, such that:

Superficial Inspection - a check for obvious deficiencies that might lead to accidents or high maintenance costs. If such deficiencies are found, immediate action is required in order to safeguard the public;
General Inspection - a visual examination of representative parts of the structure, to be undertaken at 2 year intervals after the last General or Principal Inspection;
Principal Inspection - a close examination of all inspectable parts of the structure. Normally undertaken at 6 year intervals, but to be undertaken at a minimum frequency of once every 10 years;
Special Inspection - a close examination of a particular area or defect causing concern.

4.21 BD 63/94 also introduces Acceptance Inspections of newly built structures (to be undertaken within a month of opening) and a Principal Inspection of existing structures for which responsibility is assumed, if records are not already available.

4.22 BD 63/94 states that any defect representing an immediate or imminent hazard should be treated in the same way as a Category 1 highway defect.

4.23 It is explicitly stated within BD 63/94 that standards of inspection for safety barriers and fences located at structures are contained within the TRMM (currently at Volume 2, Part 1, Chapter 1.13, February 1996).

4.24 Volume 1 of TRMM describes the inspection and recording procedures required for bridges and other highway structures.

4.25 It is stated that Maintaining Agents are responsible for keeping accurate records for all highway structures in their areas on behalf of the Highways Agency and are required to inspect all highway structures at frequencies indicated in BD 63/94.

4.26 Volume 2, Part 2 of the TRMM has been developed in order to formalise procedures for the routine maintenance of trunk road and motorway structures and to ensure that vital maintenance functions are undertaken regularly.

4.27 The document sets out the scope and frequency of operations which are to be undertaken as routine maintenance and follows on from the recommendations contained within the document "Performance Of Concrete In Bridges", authored by Maunsell Consulting Engineers in 1989.

4.28 The TRMM goes on to state that, although many of the maintenance tasks listed may be considered minor, failure to undertake them may lead to deterioration of the structure, and the need for more serious repairs in the future.

4.29 The document defines routine maintenance of structures as those activities that relate to servicing rather than repair and those that are undertaken regularly at pre-determined intervals. It is expressly stated that routine maintenance does not include the repair or renewal of structural elements or components that become unserviceable due to general wear and tear or have deteriorated for other reasons. Such repair or renewal works are required to be identified during the regular inspection process and included in planned structural maintenance programmes.

4.30 Maintaining Agents are required to prepare a schedule of routine maintenance items for each structure for which they are responsible. The schedule is then to be agreed with the Highways Agency.

4.31 Frequencies for routine maintenance activities are provided within the TRMM and are required to be adhered to "as closely as possible", although it is recognised that justified regional variation in frequency may be necessary and acceptable, subject to approval.

Carriageway Maintenance Assessment Surveys

4.32 Volume 1 of the TRMM (1992) describes the different types of maintenance assessment surveys to be undertaken on motorways and other trunk roads. It goes on to describe their extent and frequency, as well as data presentation requirements.

4.33 The document states that condition assessment data collected and analysed on a systematic and regular basis will provide the means to monitor performance and assist in the forward planning of maintenance work on the trunk road network.

4.34 In relation to asphalt carriageway surfaces (such as exhibited by the material site), the document discusses the following survey types, with each type of survey being further described and specified in other standards, as indicated below:

High Speed Road Monitor (HRM) - (DMRB Volume 7, HD 29/94, Structural Assessment Methods) - a machine survey providing data on longitudinal profile, wheel track rutting, macro-texture, curvature, cross fall and gradient. A two year cycle is to be undertaken. However, the Highways Agency have operated on an annual basis since 1998;
Computerised Highway Assessment of Ratings and Treatments (CHART) - (DMRB Volume 7, HD 29/94, Structural Assessment Methods) - a manual survey that locates specific defects (listed in the TRMM), measures and records the extent and severity of defects found and locates and records highway features (also listed in the TRMM), as necessary. A five year cycle is to be undertaken. Inspections can be either: Full, Defect or Partial. A CHART rating can be produced for each section of trunk road;
Deflectograph - (DMRB Volume 7, HD 29/94, Structural Assessment Methods) - a machine survey providing a measure of the residual life remaining in a carriageway. The data obtained from these surveys relates to structural condition. A five year cycle is to be undertaken;
Sideway-force Coefficient Routine Investigation Machine surveys (SCRIM) - (DMRB Volume 7, HD 28/94, Skidding Resistance) - providing a routine measure of the skid resistance of the surface of a road section, allowing it to be compared to a pre-determined Investigatory Level (IL) for that section. A three year cycle is required. Further information relating to SCRIM surveys is included in the following Chapter of this report.

Composition and condition of the road surfacing

5.1 This chapter concerns measurements made on the surface course of the road at the material location during the course of this investigation in order to assess the general condition of the road surfacing. Two main aspects of the road were covered, i.e. skidding resistance and surface profile.

5.2 Skidding resistance is a complex technical field. The next section of this report gives a brief description of the important issues to set a context for the discussion of the measurements made.

General Comments Regarding Skidding Resistance

5.3 When a vehicle is braking, it slows down because the kinetic energy of the moving vehicle is converted into heat energy by the brakes which, in turn, are cooled by the passing air stream. So long as the wheel continues to rotate, this process continues until the vehicle stops or the brakes are released.

5.4 However, the above process relies upon friction between tyre and road surface to provide an opposing force against which the brakes can react. When a vehicle is cornering, side forces trying to make the vehicle continue in a straight line are generated and, again, friction between the tyre and the road is needed to generate an opposing force that enables the vehicle to follow around the curve.

5.5 If the combined braking and cornering forces required are more than the available frictional force, the tyre will slide over the road surface. In the extreme case, the rotating wheel may lock and the vehicle will skid or the tyre may slide sideways.

5.6 Tyre-road friction is dependent upon a number of factors, some of these relating to the road surfacing and some to the tyre itself. Friction can also be influenced by other factors such as weather conditions and localised surface contamination.

5.7 When a road surface is dry, the coefficient of friction is normally high and adequate for most normal manoeuvres. However, when the road is wet, tyre-road friction decreases significantly.

5.8 Due to the many factors involved, it is important to distinguish between the meanings of the terms "friction" and "skidding resistance":

Friction refers to the forces that are developed between a specific tyre and a specific road at a particular time and under particular conditions. It is influenced by a large number of parameters, for example: the road, tyre and vehicle suspension characteristics, ambient temperature and presence of contaminants (including water).
Skidding resistance is the term used to describe the contribution that the road makes to the development of friction. It is essentially a measurement of friction obtained under standardised conditions in which the various parameters are controlled so that the effects of the road surface characteristics can be isolated.

5.9 As skidding resistance (and hence friction) is high in dry conditions, the term is almost always used with reference to wet roads.

5.10 Skidding resistance depends upon two characteristics of the road surfacing known as microtexture and texture depth.

5.11 Microtexture is the name given to the fine "sand-paper-like" asperities on the surface of the road. On an asphalt road, such as this part of the M62 Motorway, microtexture comes either from the crystalline structure of the stone on the surface or from sand in the asphalt mortar.

5.12 The microtexture interacts with vehicle tyres to generate the adhesive forces needed to provide friction and is the major contributing factor to skidding resistance at low speeds.

5.13 However, when the surface is wet, the microtexture also has to penetrate through the water film and so this leads to a reduction in skidding resistance.

5.14 Microtexture is gradually polished away by the action of heavy traffic so, over time, the skidding resistance of a road will fall to an equilibrium level that depends upon the number of heavy vehicles using the road and the resistance to polishing of the aggregate used in the surfacing.

5.15 In temperate climates such as Britain, the polishing process is cyclic, with skidding resistance at its lowest during the summer, recovering to some extent during the winter.

5.16 The accumulation of fine deposits on the road during long dry periods also means that, the road may be unusually slippery after the first rainfall following a long dry spell.

5.17 A road surface usually has surface texture, formed by the shape of, and the spaces around, the particles making up the surfacing. The texture depth is a measure of this. Texture is important because it provides drainage paths to allow any water on the surface to move rapidly from the tyre-road contact patch. The tyre tread assists in this process, but the greatest contribution usually comes from the road.

5.18 Texture can also generate energy losses in the tyre when it is skidding. In this process, known as "hysteresis", some of the energy that is used to deform the tyre tread when it slides over the texture is absorbed by the tyre when it returns to its original shape. These energy losses can supplement the heat exchange process in the braking system and become very important when the wheel locks and the brakes can generate no more heat.

5.19 In wet conditions, as vehicle speeds increase, skidding resistance decreases. The extent to which this occurs depends upon the texture depth. Generally, the lower the texture, the greater the loss of friction. Research conducted by TRL has shown that, in general, skidding resistance reaches a minimum level at vehicle speeds of approximately 60 miles per hour (96.6 km/h).

Measurement of Skidding Resistance and Texture Depth

5.20 The skidding resistance of road surfaces is measured in a standardised manner. There are a number of different techniques that may be used, most of which involve sliding rubber over a wetted road surface and measuring the frictional force generated in some way. On a large scale, test vehicles fitted with a special test tyre designed to be sensitive to the microtexture of the surface are used.

5.21 With these devices, the test tyre (under a known vertical load) is forced to slip over the wetted road surface and the frictional forces generated are measured. From these measurements a value that represents the skidding resistance is calculated.

Sideway-force Coefficient Routine Investigation Machine (SCRIM)

5.22 SCRIM is the device used for this purpose routinely on UK trunk road and many local authority roads. The machine uses an angled wheel with a standardised, smooth tyre which is free to rotate as the contact patch slides over the surface and generates a "sideway force" along the axle of the test wheel.

5.23 SCRIM measurements are made at a standard vehicle speed of 50km/h although, because the test wheel is rotating at an angle, the slip speed at the contact patch is 17 km/h.

5.24 After correcting for the influence of factors such as test speed, the skidding resistance as measured by SCRIM is reported as a value called SCRIM Coefficient (SC).

5.25 Due to the seasonal variation of skidding resistance, it is normal practice to characterise roads in the UK by measuring the SCRIM Coefficient three times during the summer (when the skidding resistance is likely to be at its lowest) and reporting a Mean Summer SCRIM Coefficient (MSSC).

5.26 On motorways and other trunk roads, this is currently undertaken on one third of the network each year, so that the whole network is tested on a three-year cycle.

5.27 SCRIM results obtained for a site are viewed against a pre-determined Investigatory Level (IL) for that site that is related to the risk of wet skidding accidents on that type of site.

5.28 The process of determining appropriate ILs and a table showing appropriate ILs for sites with average risk ratings is provided in HD 28/94 (Skidding Resistance), which forms part of Volume 7 of the DMRB.

5.29 Should the SCRIM results be at, or below, the IL, an investigation is required, with slippery road warning signs required to be erected whilst the investigation is conducted. A MSSC obtained above the IL requires no immediate action.

Pavement Friction Tester (PFT)

5.30 SCRIM is designed specifically for long-distance surveys at constant speed to monitor the general skid resistance levels on large networks. It measures low-speed skid resistance and essentially assesses the condition of the microtexture of the surfacing during the summer months.

5.31 Unfortunately, due to seasonal variation in skidding resistance, SCRIM is considered to be "out of season" during the months between October and April inclusive. Therefore, no standard test can be undertaken by SCRIM during these months. Also, skidding resistance changes markedly when the surface is contaminated in any way. Such contamination includes rock salt, which is commonly used to prevent ice from forming on main road carriageways during the winter months. If a road surface is salty, then once again, no standard SCRIM test can be undertaken.

5.32 It is possible to allow for such non-standard testing using SCRIM. However, the correction factors that must be applied are, by necessity, somewhat subjective in nature. When standard SCRIM testing cannot be undertaken, alternative equipment using a different measurement principle can be used to assist more detailed research or site investigation. The Pavement Friction Tester uses the locked-wheel principle to measure skidding resistance.

5.33 The PFT comprises a special trailer on which one wheel can be rapidly braked under computer control until it locks, while the vehicle continues to move at a steady speed. It is held in this state for a short time before being released ready for another test.

5.34 A standardised smooth tyre is used on the test wheel.

5.35 The load and drag forces (see Figure 5.1 below) are measured throughout the braking cycle and once the wheel has locked and settled into a skid (this normally takes about 1 second) the average friction coefficient during a further 1 second interval is calculated. The value is known as a "Friction Number" (FN).

Figure 5.1 The principle of locked-wheel skid resistance measurements

5.36 Whilst unsuited to long-distance monitoring, which is one of the reasons why this technique is not used by the Highways Agency to routinely monitor the skidding resistance of trunk roads, the above principle is useful for more detailed investigations of certain sites because it allows skidding resistance to be assessed over a range of speeds, since the value measured relates directly to the vehicle speed at the time of the test.

5.37 The test is based on an American (ASTM) standard and is widely used to assess roads in the US. In the UK, the HA acquired their PFT primarily for use in their own research programme, although the equipment is well suited for special investigations such as the subject of this report. TRL maintain and operate the PFT on behalf of the HA.

Texture Depth

5.38 Texture depth is measured either as the average level below the peaks in the surfacing, or as the root mean square deviation about a notional datum level.

5.39 The best-known method for the former approach uses a known volume of sand that is spread into a circular patch; from the average diameter of the patch, the average texture depth is calculated. This method is commonly referred to as the sand patch test. The tests are repeated along the road as required.

5.40 The second method involves calculating the texture depth from a sequence of displacement measurements of the road surface profile, usually measured using a laser device such as those fitted to the Highways Agency Road Research Information System (HARRIS) machine used in this particular investigation.

5.41 One way of processing the data is to calculate the root mean square deviation using an algorithm that filters out of longer-wavelength displacements due to movement of the vehicle chassis. Such measurements are known in the UK as Sensor Measured Textured Depth (SMTD) to distinguish them from sand patch measurements.

5.42 The values obtained from the two methods are different and their relationship varies with the surfacing type.

Surface Nature of the M62 Westbound Carriageway Around Little Heck Bridge and Visual Inspection

5.43 The road surfacing at the material stretch of the M62 Motorway comprises standard hot-rolled asphalt with pre-coated chippings, laid across hard shoulder and all three running lanes. As discussed earlier in this report, the pertinent section of the westbound carriageway appears to have last been resurfaced in 1993.

5.44 Visually, the surfacing appears to be in good order, with a good coverage of chippings and no evidence of significant chipping loss or marked wheel-path rutting.

5.45 A visual comparison of the hard shoulder with the running lanes showed a clear difference in the character of the surfacings in the running lanes, due to trafficking, as would be expected. The chippings on the main carriageway (especially in Lane 1) showed obvious signs of polishing action and have been rounded by the abrasive action of traffic over the years.

5.46 In temperate climates, such as the UK, the process by which heavy traffic polishes the road surface material is cyclic, with skidding resistance being normally at its lowest during the summer months, recovering to some extent during the winter. Fine dust collects on the surface during the drier summer months, which then acts as a medium to accelerate the polishing of the aggregate by vehicle tyres. During the winter, more frequent rain disperses the fines and increases the quantity of "gritty" particles on the road surface. Combined with the action of vehicle tyres, these tend to roughen the surface again.

5.47 This effect is known as "seasonal variation" and gives rise to a "polishing cycle". Although the extent of the fluctuation in skidding resistance can change depending on the actual prevailing conditions, under constant traffic levels the skidding resistance eventually reaches an equilibrium cycle which is maintained for many years of service.

5.48 The accumulation of fine deposits on the road during long dry periods also means that the road may be unusually slippery after the first rainfall following a long dry spell. This effect is in addition to the seasonal effect and is caused by the contaminating effect of the dust and oil that mixes with the water to form a thin slurry on the surfacing, until it is washed away by the rain.

5.49 The month of March each year is towards the end of the winter recovery period of the polishing cycle. As would be expected at this time of year, the chippings looked, and felt to the touch, less "polished" than they might in mid-summer.

5.50 On the hard shoulder, the angular "crusher-run" edges of the chippings remained and the binder film, although well weathered, was still in evidence. This was most noticeable on sections that had been wetted during the testing, where the natural colouring of the aggregate showed through on the more-trafficked areas.

5.51 At the time of the tests there was a scattering of undissolved salt crystals on the surface of the road. Any effect that this might have had on the measurements would have been very small.

Measurements of Skidding Resistance

5.52 Skidding resistance measurements were made on 4 and 5 March 2001 by specialist teams from TRL. The Highways Agency's Pavement Friction Tester was used for these tests. Texture depth was measured using laser sensors on the HARRIS vehicle.

5.53 The section of surfacing included in the assessment of skidding resistance was a 500 metre length of the westbound carriageway of the M62 Motorway leading to the bridge over the East Coast Main Line (ECML). The sections studied were identified by means of the motorway marker posts, the measurements reported here being made at various points between Marker Posts 146.6 and 146.1.

5.54 The marker posts are used here to define the position of the measurements on the road, often referred to as a "chainage". The chainage is usually measured from a fixed point at one end of the road and so it usually increases in one direction of travel and decreases in the other.

5.55 On motorways, chainages are shown by marker posts placed every 100 metres at the carriageway edge. Each marker post has a number giving the number of kilometres from a reference point and, underneath it, the number of 100 metre sections along the current kilometre.

5.56 On the M62 Motorway, the chainage is measured from its western end, so the numbers on the marker posts on the westbound carriageway decrease in the direction of traffic. For example, the parapet of Little Heck Bridge begins at MP146.1. Chainage 146.200 to 146.100 represents the 100 metres immediately before the bridge parapet.

5.57 It has been established that the nearside wheels of the Land Rover initially left the hard shoulder and mounted the kerb road approximately 50 metres from the start of the safety fence protecting the bridge parapet. This point is approximately 90 metres from the start of the bridge parapet, i.e. at a chainage of 146.19.

5.58 The marks on the grass verge indicate that the vehicle left the road at a shallow angle, approximately 5 degrees to the line of the kerb. Assuming the vehicle had followed an approximately straight path before arriving at this point it is possible to estimate the distance that it would have covered between leaving Lane 1 and hitting the kerb.

5.59 It is reasonable to assume that the vehicle had (at least for a time) travelled in the normal wheel paths in Lane 1. This would position its nearside wheels approximately 3.5 metres from the kerb. Therefore, for an angle of approach of between 3 and 6 degrees, it would have travelled approximately between 30 and 70 metres along the road while moving to the left.

5.60 Therefore, the main area of interest from a skidding resistance viewpoint lies between chainages 146.26 and 146.19. However, it is also important to consider this length in the context of the general condition of the road and therefore, measurements were made over a rather longer length than this.

5.61 During the period when the tests were made, a system of traffic management was in place, diverting live traffic into one or both of the overtaking lanes (Lanes 2 and 3). For this reason, measurements with the PFT were confined to Lane 1 and the hard shoulder.

5.62 A police incident room was established on the railway bridge, obstructing the hard shoulder and limiting the lane width in Lane 1. Furthermore, the section of the hard shoulder immediately adjacent to the point where the material vehicle left the road and mounted the grass verge was cordoned off from MP 146.2 onwards.

5.63 For these reasons, it was not possible to make skidding resistance measurements using the PFT on the hard shoulder throughout the whole length of the area of specific interest, especially at the higher speeds.

5.64 However, despite the above, it is considered that the results obtained using the PFT provide sufficient coverage to provide a detailed opinion on the condition of the road surface at the location around the material time.

Test Methodology

5.65 The pavement friction tester (PFT) was used to measure locked-wheel friction at two speeds, nominally 20 km/h and 100 km/h respectively, in the nearside wheel path of both Lane 1 and the hard shoulder.

5.66 The slower speed represents a similar slip speed to that used by SCRIM when operated at 50 km/h and is known to relate to those measurements. This type of low-speed measurement can be used to assess the underlying condition of the microtexture.

5.67 The higher speed gives a direct indication of skidding resistance at higher vehicle speeds and can be used to confirm the influence of texture depth on skidding resistance.

5.68 Before making any skidding resistance measurements, the calibration of the distance recording system on the PFT was checked by measuring the distance recorded between marker posts over three different 1 km lengths on the eastbound carriageway.

5.69 The computer system on the PFT was set to operate in "continuous lock-and-release" mode. Using this approach, a pattern of tests can be initiated at a fixed reference point (MP 146.6 was used) and the system locks the test wheel, records the forces, releases the brake to allow the test wheel to rotate again before automatically repeating the braking cycle.

5.70 Operating in this mode, the watering system delivers a controlled flow just in front of the test tyre. The flow rate is regulated by the vehicle speed and is designed to deliver a nominal water film thickness of 1 mm.

5.71 This process results in a sequence of locked-wheel wet skids at approximately five second intervals. The length of the skid over which measurements are made lasts for 1 second, covering a distance of approximately 5 metres at 20 km/h and 28 metres at 100 km/h.

5.72 Eight passes were made, two at each target speed in each lane. The actual speeds achieved were slightly different, but close to, the target speeds. Measurements in Lane 1 were started at MP146.4. Due to the restrictions in the hard shoulder, measurements were started there at MP 146.6.

Test Results

5.73 The results of the tests are shown in graphical form in Figure 5.2 below. This figure shows the individual skids and, in addition, the texture depth recorded by HARRIS.

Figure 5.2 - PFT Test Results

Click to enlarge graph

5.74 As can be seen in Figure 5.2, the skidding resistance at higher speeds (depicted by the longer "dashes" on the graph) is well below that at lower speeds (depicted by the shorter "dashes" on the graph) both in Lane 1 and on the hard shoulder. This relationship is normal and to be expected.

5.75 The repeat passes at each speed can also be seen to be very similar to one another.

5.76 At low speed, the hard shoulder had slightly higher skidding resistance than Lane 1. This is as would be expected from the relatively untrafficked lane.

5.77 As also would be expected on a road of this type, skid resistance is consistent along the road.

5.78 There is rather greater variation in the hard shoulder; this is to be expected from the untrafficked nature of the surfacing.

5.79 The hard shoulder shows a greater fall in skidding resistance at the higher speed than Lane 1. This is consistent with the lower texture depth observed on the hard shoulder, although, because it starts from a higher level, the general level of high speed skid resistance is similar to Lane 1.

5.80 The texture depth in Lane 1 is considered to be at a good level (1.53 mm on average) while the hard shoulder exhibits a lower, but still acceptable level (0.74 mm on average). Routine texture depth measurements taken on a trafficked lane of motorway would need to be less than 0.5 mm in order for it to warrant investigation (DMRB Volume 7, HD 29/94, Structural Assessment Methods, refers).

Comparison of Results with Standards

5.81 The requirements for the skidding resistance of motorways are set out in Chapter 3 of Volume 7 of the Highways Agency Design Manual for Roads and Bridges. This defines the Investigatory Level for the MSSC in Lane 1 of a main line motorway as 0.35.

5.82 The road at the material location was last tested by SCRIM during the summer of 1998 (therefore, it is due for a repeat test in the summer of 2001). The results from the 1998 tests have been obtained and the measurements for the relevant section of road have been extracted.

5.83 Utilising an empirically derived conversion process obtained from research work carried out at TRL it is also possible to make an estimate of the SCRIM coefficient represented by the slow-speed measurements from the PFT.

5.84 These results, expressed as average values over successive 50 metre lengths have been calculated and are given in Table 5.1 below.

Table 5.1 - Summary of SCRIM and PFT Measurements

Marker post chainage at start of each 50m section	Lane 1			Hard Shoulder
Marker post chainage at start of each 50m section	MSSC measured in 1998	mean FN x 100 at 21km/h	Approx. SC	mean FN x 100 at 21km/h	Approx. SC
146.600	0.44	-	-	64.8	0.50
146.550	0.43	-	-	65.6	00.50
146.500	0.43	-	-	61.3	00.48
146.450	0.44	-	-	64.8	00.50
146.400	0.43	58.5	0.46	63.2	00.49
146.350	0.43	59.1	0.46	063.7	00.49
146.300	0.43	59.5	0.47	0-	0-
146.250	0.43	58.9	0.46	0-	0-
146.200	0.43	60.0	0.47	0-	0-
146.150	0.42	61.5	0.48	0-	0-
Average	0.43	59.6	0.47	063.9	00.49

5.85 The SCRIM measurements obtained in 1998 were all above the Investigatory Level, which was appropriately set at 0.35, and therefore fully complied with the requirements of the Highways Agency standards at that time.

5.86 In 1998, the surfacing was approximately five years old and would have been expected to have reached its equilibrium skid resistance level.

5.87 The measurements made with the PFT in March 2001 show that the skidding resistance of the road at the material time remains at a good level and exceed the appropriate Investigatory Levels by a considerable margin. The estimated values for the SCRIM coefficient at the site are higher than the MSSC measured in 1998, as is to be expected with a late winter measurement. The results obtained are considered to be consistent with what would be expected on this type of road at this time of year.

5.88 It should be noted that there are currently no specific in-service requirements for texture depth on this type of road. However, the texture depth measurements indicate a level that past research has shown to be acceptable.

5.89 The PFT measurements at higher speed confirm that the texture is performing as would be expected. The results from the surfacing at the material location are considered to be entirely consistent with those found from research on similar surfacings elsewhere in the UK.

5.90 In summary, the skidding resistance of the road at the material location met or exceeded all the requirements of the Highways Agency standards.

Carriageway profile

6.1 An extremely detailed survey of the 600 metre section of the westbound carriageway of the M62 Motorway between Marker Posts 146/9 and 146/2 (i.e. the immediate approach to Little Heck Railway Bridge) was undertaken on 4 March 2001 using the Highways Agency Road Research Information System (HARRIS) survey vehicle.

6.2 Continuous measurements of the following parameters were made in the hard shoulder and the first running lane (Lane 1):

Global Position and Curvature - to determine the carriageway alignment / straightness;
Altitude - to determine the height of the carriageway above / below a set datum;
Gradient - to determine the gradient of the carriageway;
Crossfall - to determine the transverse fall of the carriageway;
Sensor Measured Texture Depth - to determine the macrotexture of the carriageway surface;
Variance - to determine the ride quality of the carriageway surface;
Rutting - to determine the depth of any carriageway rutting.

6.3 The survey runs were repeated to ensure that the accuracy of the measurements was of a high standard.

6.4 The data obtained can be analysed at intervals of any multiple of 1m. However, for assessment of pavement condition on a Network level it is common for results to be aggregated into 100 metre lengths. This has been done with the data obtained from the M62 motorway, with the data being tabulated and included at the end of this section of this report.

6.5 The conclusions that can be reached from the HARRIS data obtained are as follows (with reference, as applicable, to threshold values and categories contained within technical standard HD 29/94, which can be found within Volume 7 of the DMRB):

The variation in the measured parameters along the length of the 600 metre section can be shown to be no different from the variation that would be typically obtained along the length of a sound carriageway surface;
There is no evidence of any extremes of longitudinal or transverse profile or unacceptable profile shape, when examined in comparison with profiles typically recorded on motorways and other trunk roads.
With reference to the requirements of the DMRB it can be seen that acceptable levels of carriageway rutting and ride quality (variance) are obtained. The ride quality is considered likely to fall into the upper quartile of sites (if not better);
There is no evidence of any extremes in carriageway rutting. Rutting in the nearside wheeltrack is of a greater magnitude than that found in the offside wheeltrack. This is not untypical of the rutting generally found on the English motorway and trunk road network. Rutting in Lane 1 increases as the site of the bridge is approached. This may be related to the slight incline in the carriageway at this point, as increased vehicular loading on inclines is a well known phenomenon that can lead to an increased propensity for rutting to develop in the wheeltracks. None of the rutting found at the site can be considered deep or unacceptable;
Texture Depth has been commented on in Chapter 5 of this report;
The crossfall of the carriageway is consistent with that generally found on straight UK Motorways and Trunk roads at 2 - 2.5%;
There is a steady incline at the site with a gradient of approximately 1.5%. This level of incline can be considered slight, and is by no means high it terms of the inclines that can be experienced on UK Motorways and Trunk Roads;
The curvature readings taken on the site show a radius exceeding 2000 metres, i.e. the site is effectively straight in alignment.

6.6 The HARRIS survey data from the Little Heck site are shown in Appendix 1 of this report.

6.7 In summary, the HARRIS data obtained shows that the westbound carriageway of the M62 Motorway between Marker Posts 146/9 and 146/2 exhibits no extremes in alignment, gradient, profile or rutting and is indicative of a sound carriageway surface.

Vibra-Line ("Rumble Strip") Provision

6.8 As stated in Chapter 3 of this report, the edge line marking between the hard shoulder and Lane 1 of the westbound carriageway at the material location consists of vibra-line, which is sometimes referred to as a "rumble strip", as it creates an audible warning to drivers when their vehicles leave the traffic lanes.

6.9 The requirements for road markings are given in Statutory Instrument No. 1519 "Traffic Signs Regulations &General Directions 1994", which came into force on 12 August 1994. This document specifies road markings by reference to various diagrams, with longitudinal edge markings shown in Diagram 1012.1.

6.10 Diagram 1012.2 shows an "alternative to the marking shown in diagram 1012.1 incorporating an audible and tactile warning in the form of a raised rib for use on motorways" and specifies the requirements for vibra-line/rumble strip.

6.11 Such markings consist of continuous white lines approximately 200 mm wide incorporating transverse ribs which are approximately 50 mm long and raised by 9 mm above the adjacent surface of the marking. The raised ribs are provided at intervals of approximately 500 mm.

6.12 The inspection and maintenance of road markings is carried out under the procedures described in the following Chapter of this report.

Routine highway maintenance

7.1 As previously stated within this report, WSP Civils Limited are responsible for managing the maintenance of the material section of the M62 Motorway on behalf of the Highways Agency to the requirements of the pertinent Trunk Road Maintenance Manual, issuing instructions to Carillion Highway Maintenance Limited, the Term Maintenance Contractor.

Safety Inspections

7.2 Records provided by WSP Civils Limited show that Safety Inspections are being consistently undertaken on the material section of the M62 Motorway at the weekly frequency required by the Trunk Road Maintenance Manual.

7.3 It appears that Safety Inspections of this road are consistently undertaken on the Wednesday of each week. This means that a Safety Inspection was undertaken on the day of the material accident (28 February 2001).

7.4 The following Safety Inspections were undertaken at the location in the month prior to the material accident:

Date	Weather Conditions	Road Surface Condition
31 January 2001	Fine	Dry
7 February 2001	Fine	Dry
14 February 2001	Fine	Dry
21 February 2001	Fine	Dry
28 February 2001	Fine / Rain	Wet

7.5 The data relating to Safety Inspections is retained in a computerised recording system, such that each section of carriageway has a unique identifier. The section of the westbound carriageway of the M62 Motorway that includes Little Heck Bridge and its approach is referred to as Link 1 Section 15.

7.6 Records of the Safety Inspections undertaken in the month prior to the material accident show that no safety related defects were identified on the material section of road at those times.

7.7 The time of day that the 28 February 2001 Safety Inspection was undertaken is not recorded. However, it is considered most likely that the inspection would have been undertaken after the material accident had occurred and at some time following the morning peak traffic period.

Detailed Inspections

7.8 In the production of this report, the records relating to the last Detailed Inspections undertaken prior to the material accident have been considered.

7.9 These comprise:

Detailed Inspection of the carriageway undertaken on 14 December 2000;
Detailed Inspection of safety fences on 7 July 2000;
Detailed Inspection of the highway boundary fence on 23 February 2001.

7.10 The above Detailed Inspection of the carriageway was undertaken in fine weather conditions, with a wet road surface. No defects were recorded on the pertinent section (Link 1 Section 15).

7.11 The records of the Detailed Inspection of the safety fences show that the inspections were undertaken in fine, dry conditions. No defects are recorded for the "steel-tension safety fence" (inspection code FN in the RMMS) present in Link 1 Section 15. 4 no. defects (comprising 2 no. missing foam pads and 2 no. missing washers are recorded for the "safety fence - metal / concrete" (inspection code FB in the RMMS) present in Link 1 Section 15. However, these defects are minor in nature (i.e. their replacement would constitute routine maintenance works) and are considered irrelevant in terms of the incident involving Mr Hart.

7.12 The records of the Detailed Inspection of the highway boundary fence show that the inspection was undertaken in fine weather and that four damaged rails were present in the boundary fence between Marker Post 146/7 and Marker Post 146/3 + 35 metres. This area is some 600 to 235 metres to the east of the Little Heck Bridge, which is adjacent to Marker Post 146/1. It is considered that these defects are irrelevant in terms of the incident involving Mr Hart.

7.13 As can be seen from the above, it is evident that a Detailed Inspection of the carriageway was undertaken approximately two and a half months prior to the occurrence of the material incident, a Detailed Inspection of the safety fence was undertaken approximately eight months prior to the material accident, and a Detailed Inspection of the boundary fence was undertaken less than a week before the material accident. These are all shorter periods of time than the required intervals for such inspections (as discussed in Chapter 4 of this report).

Safety Patrols

7.14 Daily Safety Patrol Records provided by WSP indicate that the last Safety Patrol undertaken at the material location prior to the accident appears to have taken place shortly after 0838 GMT on 27 February 2001. No safety defects were recorded during this patrol.

7.15 It appears that no Safety Patrol was conducted at the material location on the day of the accident. However, this to be expected, as a Safety Inspection appears to have been undertaken on that date and, as stated earlier in this report, Safety Patrols are only required on dates between Safety Inspections.

Debris Lists

7.16 Debris lists schedule the date, location, time and description of debris found on the highway during routine inspections or debris that has been brought to the attention of the maintaining engineers by other means. Debris listed typically includes: tyre shreddings, dead animals, oil spillages or material fallen from HGVs etc.

7.17 The debris list for the M62 Motorway during the end of February 2001 shows two entries for 26 February 2001. However, neither of these entries relates to the vicinity of the material location. No entries are shown for 27 or 28 February 2001.

Gully Emptying

7.18 A WSP works order, dated 23 June 1999, refers to the cleansing of all nearside drainage gullies and catchpits between Junctions 34 and 38 on the eastbound and westbound carriageways of the M62 Motorway. This includes the section around Little Heck Bridge. It appears from this order that these works were instructed to commence from 16 August 1999 and be completed by 14 September 1999.

7.19 It appears that the gullies on the westbound carriageway of the M62 Motorway in the vicinity of Little Heck Bridge were cleansed on 16 September 1999.

7.20 A further WSP works order, dated 17 May 2000, refers to the cleansing of the same schedule of nearside gullies and catchpits. Works were instructed to commence from 22 May 2000 and be completed by 2 July 2000.

7.21 It appears that the above works commenced on 12 June 2000 and were completed on 8 August 2000.

7.22 From the above information, it appears that gully emptying at the material location has been undertaken in accordance with the standard recommended annual cleaning frequency as detailed within the Trunk Road Maintenance Manual (Volume 2, 1996).

Hard Shoulder Sweeping

7.23 Records have been provided relating to the sweeping of the hard shoulder of the westbound M62 Motorway between Marker Posts 149/3 and 142/0 on 15 February 2001. This section includes the immediate vicinity of Little Heck Bridge.

7.24 Therefore, it appears that the hard shoulder was swept less than a fortnight before the incident under investigation occurred.

7.25 It appears that previous sweeping operations have also taken place on this section in August 2000 and November 2000.

Sideway-Force Coefficient Routine Investigation Machine (SCRIM) Surveys

7.26 A SCRIM survey was undertaken at the material location in the summer of 1998.

7.27 The three-year cycle for SCRIM surveys would lead to the next routine SCRIM survey of the material location taking place during the summer season of 2001.

7.28 SCRIM testing on motorways is typically restricted to the first running lane (Lane 1) and this appears to have been the case with the pertinent surveys.

7.29 The results of the 1998 SCRIM survey have been discussed in Chapter 5 of this report. As reported, the MSSC values obtained were all well above the minimum requirement for satisfactory wet skid resistance.

High-Speed Road Monitor (HRM) Surveys

7.30 An HRM survey was last undertaken at the material location on 10 August 1999. Since then a routine survey has been carried out under the Highways Agency's TRAffic speed Condition Survey (TRACS) programme in October 2000. The data from this survey is currently unavailable. However, the data obtained from the HARRIS survey undertaken at the site as part of TRL's investigation includes similar parameters and provides measured values taken only a few days after the incident.

7.31 The 1999 HRM tests were conducted in Lane 1 of the westbound carriageway and, for the final 281 metres of Link 1 Section 15 (which includes the Little Heck Railway Bridge, located towards the end of the section), they indicate:

Length (m)	Texture (mm)	Rut Depth (mm)
Final 81	1.11	2.2
"Middle" 100	1.35	1.8
"First" 100	1.54	2.67

7.32 As previously stated, carriageway texture depth is important to assist in providing skidding resistance on wet road surfaces. It is a particularly important factor in providing skidding resistance to high speed traffic. Texture depth on trafficked carriageways is typically of the order of 1 millimetre deep and, during a routine survey, texture depth would have to be measured at 0.5 mm or less in order for further investigations to be warranted (DMRB Volume 7, HD 29/94, 1994).

7.33 Experience indicates that longitudinal wheeltrack rutting typically only becomes of concern if it exceeds depths of well in excess of 10 millimetres.

7.34 Therefore, the data from the 1999 HRM survey of the material site indicate that texture depth and rut depth would have provided no cause for concern.

7.35 The data from the HARRIS survey undertaken as part of this investigation are discussed earlier in this report.

Deflectograph Surveys

7.36 Deflectograph surveys are designed to assess the residual life of a carriageway and therefore the data relate to the underlying structural condition of the road. This information is important for maintenance planning purposes, but is less important in relation to safety, unless the road is at the end of its life and is actually breaking up.

7.37 A deflectograph survey was last undertaken at the material location on 14 October 1999 and WSP have indicated that the next survey is scheduled for 2003. This is consistent with the five year cycle for deflectograph surveys referenced within the Trunk Road Maintenance Manual (Volume 1, 1992).

7.38 The results from the 1999 deflectograph survey show a residual life for the section of westbound carriageway including Little Heck Bridge (Link 1 Section 15) of at least a further nine years. Therefore, these results support the opinion that there are no structural problems with the carriageway at this site.

CHART Surveys

7.39 A CHART survey was last undertaken at the material location on 29 July 1998 and WSP have indicated that the next survey is scheduled to take place in 2002. This is consistent with the five year cycle for CHART surveys referenced within the Trunk Road Maintenance Manual (Volume 1, 1992).

7.40 The CHART results obtained in 1998 for the section of westbound carriageway in the immediate vicinity of Little Heck Bridge (the western end of Link 1 Section 15) indicate:

A consistent carriageway width of 10.9 metres (i.e. three running lanes each with a nominal standard width 3.65 metres) and central reserve width of 10 metres;
Wheel track rutting of magnitude 2-3 mm;
A continuous kerb with an upstand of 78 mm;
3 no. carriageway patches.

7.41 These data are consistent with the data obtained from other surveys and again indicate that there is no cause for concern regarding road surface condition at this site.

Summary

7.42 From all of the routine maintenance information seen in the preparation of this report, it is considered that the pertinent section of the westbound carriageway of the M62 Motorway is being maintained in a responsible manner by WSP Civils Limited on behalf of the Highways Agency and generally in accordance with the requirements laid down in the Trunk Road Maintenance Manual.

7.43 The inspection, defect and condition survey information from the routine maintenance operations undertaken recently do not indicate any problems being encountered that could be pertinent to the incident under investigation.

Winter maintenance

Weather and Road Surface Condition

8.1 In the preparation of this report, weather data has been obtained from the Highways Agency's automated weather station on the M62 Motorway at High Eggborough (located approximately 3.2 kilometres (2 miles) to the west of the material location) for 28 February 2001.

8.2 This data shows that, between 0000 GMT and 0620 GMT on 28 February 2001, i.e. for the period encompassing approximately six hours preceding the material accident, the air temperature fell relatively consistently from +2.4°C at 0000 GMT to +0.5°C at 0620 GMT.

8.3 The data indicates that light rain was falling at the station during the periods 0020 GMT to 0120 GMT, 0240 GMT to 0300 GMT and 0420 GMT to 0720 GMT.

8.4 There are two road surface temperature sensors at this station. The road surface temperature at one of these sensors fell steadily from +3.5°C at 0000 GMT to +2.1°C at 0600 GMT and then relatively rapidly decreased to +1.6°C at 0620 GMT. The surface temperature recorded by the other sensor at this site fell more erratically, reaching a minimum of +0.8°C at 0520 GMT and then rising to +1.2°C again by 0620 GMT.

8.5 The sensing equipment is also capable of measuring road condition at the surface sensors, i.e. whether the road was dry, wet, icy or salted (although the method utilised to determine salinity levels cannot record the presence of salt on a dry surface and commonly underestimates the amount of salt present at other times). Both surface sensors at High Eggborough indicate that salt was present on the material carriageway during this period

8.6 In the preparation of this report, data from the weather stations on the A1(T) at Barnsdale Bar and the M18 at Hatfield has also been obtained. These stations are located in the general area of interest but further away from Little Heck Bridge than High Eggborough.

8.7 These data indicate:

For Barnsdale Bar: lowest air temperature +0.3°C at 0600 GMT; light rain recorded at 0100 GMT, 0500 GMT, 0600 GMT and 0700 GMT; lowest road surface temperature +0.8°C at 0700 GMT;
For Hatfield: lowest air temperature +0.7°C at 0700 GMT; light rain recorded at 0100 GMT and 0300 GMT; lowest road surface temperature +1.4°C at 0600 GMT.

8.8 Both these stations recorded the presence of residual salt during this period.

8.9 TRL has been informed that, at 0725 GMT on 28 February 2001, i.e. some 70 minutes after the accident involving Mr Hart, the road surface condition at Little Heck Bridge was found by a WSP engineer to be damp and that no snow was present.

8.10 On the basis of all of the information discussed above, it appears unlikely that the surface of the M62 Motorway at Little Heck Bridge was adversely affected by ice or snow at the time of Mr Hart's accident.

8.11 However, in view of the fact that the cause of the vehicle leaving the carriageway is currently unknown and it is possible that the Police investigations will comment on road surface condition, the following sections discuss the winter maintenance procedures adopted by the maintaining engineers and provide opinion regarding their adequacy.

Highway Winter Maintenance Methodology

8.12 The primary method of preventing the formation of frost and ice on road surfaces during freezing periods is to spread salt from purpose built vehicles. These are equipped with a hopper and a spreader mechanism, which can regulate both the rate of spread and the spread pattern so that the whole of the road surface can be treated with the correct amount of salt.

8.13 Salt in solution freezes at a lower temperature than water alone and if spread before the onset of freezing conditions can be effective in preventing ice from forming on road surfaces at temperatures down to below -10°C.

8.14 However, salt is only effective in this role if it can form a solution with the water on the road surface. If this water has already frozen before the salt is applied the salt is much less effective in combating the slippery conditions. Occasionally therefore, sand is included with the salt as this, in conjunction with the action of vehicle tyres can aid both grip and the break up of existing ice.

8.15 Due to various reasons, including the blocking of drainage channels and the problems it causes after the ice hazard has passed, grit of a particle size greater than sand is no longer used on UK roads for this purpose. However the generic term "gritting" is often used to describe what is actually "pre-salting" or "precautionary salting", i.e. spreading salt before the onset of ice and frost formation. This is the primary method of dealing with freezing conditions on roads across the UK.

8.16 Depending upon whether precipitation is forecast, typical rates of spread of salt when pre-salting range from 10 to 20 grammes per square metre (g/m2 ).

8.17 Post-salting applications, i.e. those undertaken in order to aid the break up and removal of snow and ice from the carriageway surface once it has formed, is less efficient and typical rates of spread when post-salting are between 20 to 40 g/m2.

Winter Maintenance Standards

8.18 The document that details the standards to which the pertinent section of the M62 Motorway is to be maintained during winter conditions, is Part 3 of Volume 2 of the Trunk Road Maintenance Manual (1996).

8.19 This document includes a Statement of Service in respect to the winter maintenance of trunk roads and motorways, stating: "The Highways Agency aims to provide a winter maintenance service which, as far as possible, allows the safe movement of traffic on motorways and all-purpose trunk roads (APTRs) in England, and keeps delays and accidents caused by adverse weather to a minimum".

8.20 The TRMM goes on to state that Maintaining Agents are required to undertake the operational management of the winter maintenance service on behalf of the Highways Agency.

8.21 For operational purposes, the TRMM divides the winter season into three periods:

(i) High, i.e. the months of December, January and February, when severe conditions are described as probable;
(ii) Low, i.e. November and March, when severe conditions may occur.
(iii) Marginal, i.e. October and April, when severe conditions would not be expected.

8.22 It can be seen from this that the date of the material accident, 28 February 2001, is just within the "High" period.

8.23 It is also stated that treatment routes and shift arrangements must be organised to allow defined standards of Response and Treatment Times to be achieved.

8.24 The Response Time is defined as the time taken from the decision to begin treatment until the winter maintenance vehicles are loaded, manned and ready to leave the compound.

8.25 The Treatment Time is defined as the time taken from leaving the compound, in order to begin the treatment of the trunk roads for which the Maintaining Agent is responsible, through to completion of the treatment.

8.26 The TRMM stresses that precautionary treatment of motorways and other trunk roads shall be undertaken within a maximum Response Time of 1 hour and a maximum Treatment Time of 2 hours. Therefore, the winter maintenance system developed must be capable of achieving a Total Treatment Time of 3 hours, when necessary. The Total Treatment Time being defined as the period between taking a decision to undertake an immediate precautionary salting operation and the time when the salting routes have been completed.

8.27 Anticipating ice forming or snow settling on the road surface, and then reacting correctly, will depend upon a mixture of local knowledge and experience, good weather forecasts and an awareness of the current condition of the road (i.e. whether it is wet or dry and/or whether any residual salt from previous treatments is sufficient to mitigate against anticipated weather conditions). The TRMM recommends that Maintaining Agents make full use of specialised road weather forecasting services offered by meteorological organisations for this purpose.

8.28 The document contains the following guidance:

"A decision to treat [salt the road] will depend upon many factors but if road surface temperatures are predicted to fall below plus 1°C a precautionary treatment should normally take place unless:

(a) no moisture is on or is expected to be on the road; or
(b) there is sufficient residual salt on the road to deal with the expected conditions "

8.29 The TRMM warns that elevated sections of road, including bridges, and sections lying in low ground or where the topography channels wind-borne cold air, are more prone to freezing and may need special attention.

8.30 For precautionary salting operations, the TRMM recommends that barn stored salt should be spread at 10 g/m² and salt stored in the open at up to 20 g/m². This rate should be increased to between 20 and 40 g/m² if freezing conditions are expected after rain, or continuous snowfall is forecast.

8.31 For post salting operations (i.e. when ice or snow has already formed), the TRMM recommends that salt be spread at up to 40 g/m² to ensure a rapid melt. Post salting treatments can be undertaken in association with physical ploughing.

8.32 The TRMM recognises that road conditions can change very quickly over relatively short distances and states that this stresses the importance of effective liaison between the Maintaining Agent, Contractor, the weather forecast provider, the Police and other emergency services, the media, public transport operators and various road user groups. Maintaining Agents are also encouraged to actively liaise with the local Police patrols regarding road conditions.

The System Of Winter Maintenance Operated By The Maintaining Agent

8.33 WSP's "Winter Maintenance and Other Emergencies" Plan, dated November 2000 was in effect at the time and location of Mr Hart's accident.

8.34 The introduction to this Plan states:

"This document has been prepared as a guide and describes the Winter Maintenance Procedures for the Area 16 Motorway and Trunk Road Network and has been compiled in conjunction with the "Trunk Road Maintenance Manual: Volume 2, Part 3 Winter Maintenance Code" published by the Highways Agency."

8.35 The Plan also covers the call-out procedure for all other types of highway emergency, i.e. it does not just concern winter maintenance activities.

8.36 The Plan states that WSP have operational staff at three motorway compound offices (known as Sub-Area Control Offices), based at Tingley, Aston and West Cowick. Each office is responsible for operational and maintenance functions for their particular sub-area.

8.37 It is stated that each of the three sub-area offices possesses a Winter Duty Officer and a named Deputy, who operate in the role during normal hours (0800 to 1700 hrs, Monday to Friday). Outside of normal hours, a Duty Standby Officer assumes responsibility for receiving any weather forecast updates and taking any necessary out-of-hours winter maintenance decisions.

8.38 The Plan states that Carillion are responsible for effecting winter maintenance operations (i.e. implementing the instructions of WSP).

8.39 A total of nine operational compounds are used across the area by WSP, including the location of the Sub-Area Offices at Aston, Tingley and West Cowick.

8.40 It is stated that Carillion "organises" salting and ploughing from each of the nine compounds using pre-determined salting routes and following instructions issued by WSP.

8.41 Of winter maintenance labour, the Plan states that necessary cover is obtained by utilising operatives on Standby (at home or at the compound), or by Normal or Continuous Shifts.

8.42 The Plan clearly states that "only experienced personnel will be employed outside normal shifts".

8.43 The following shift definitions are provided:

Normal - On duty based at the compound during normal working hours;
Continuous - On duty based at the compound 24 hours;
Standby - Personnel available at the compound no more than one hour after being called out from elsewhere or from home;
Call Out - Off duty personnel available for duty as demand arises.

8.44 The above is consistent with requirements of the TRMM.

8.45 The Plan clearly indicates that WSP operate to a one hour Response Time and a two hour Treatment Time, which is in accordance with the TRMM.

8.46 The Plan states that winter weather forecasts are received daily at the Sub-Area Offices (at Aston, Tingley and West Cowick) between 1300 and 1430 GMT, via the Vaisala TMI Computer Bureau, based in Birmingham.

8.47 It is understood that copies of forecasts received are held at each Sub-Area Office. The Plan states that site specific forecasts are received for five of the area's 11 automated weather/ice prediction station sites. It is acknowledged that forecast updates may be issued or received at any time.

8.48 However, it is also stated that, in the absence of a forecast for any reason, precautionary salting would take place when temperatures reached +1°C and were falling, provided that prevailing humidity, residual salt levels and cloud cover were consistent with such a decision. This is consistent with the TRMM.

8.49 With respect to the rate of spread of salt to be adopted, the Plan states:

"For precautionary salting, treatments shall be carried out at the minimum rate of 10 g/m sq. These rates may be increased up to 20 g/m sq, according to the amount of humidity expected and the carriageway construction.

If ice has formed on the road surface salt should be spread at the rate of up to 40 g/m sq depending upon the amount of ice to be removed and the temperature. On receipt of a forecast of snow, pre-salting should be carried out at 20-40 g/m sq according to the anticipated severity of the snowfall"

8.50 The above rates of spread are consistent with those contained within the TRMM.

8.51 The Plan recognises the operational problems associated with undertaking precautionary salting operations in peak hour traffic conditions, stating that:

"Generally, morning salting runs must be completed by 07:00hrs and evening salting should not commence until 20:00hrs"

8.52 The Plan states that, once a decision has been reached to undertake a precautionary salting operation, WSP will notify adjoining Maintaining Agents by facsimile during working hours. A specimen facsimile notification is provided within the Plan.

8.53 The Plan states that Highways Agency owned salting vehicles (comprising of front line operational vehicles and reserve vehicles) have been allocated to the various compounds across the area.

8.54 It appears that all salt used for winter maintenance on the M62 Motorway is stored undercover.

8.55 The Plan also contains various maps and schedules showing salting routes, fleet profiles and the location of automatic weather / ice prediction out stations and sub-area compounds. With respect to the westbound carriageway of the M62 Motorway at Little Heck Bridge, the Plan contains the following information:

This location lies within the Humberside Sub-Area, which is administered from West Cowick Maintenance Compound/Sub-Area Office;
It is included within Salting Route R20, which is serviced from the West Cowick Maintenance Compound. The route is given the radio call sign "Cowick Gritter 1" and is serviced by salting vehicle index number L602 GYP. The schedule for the route indicates that the route should take 1 hour to complete, with 48 minutes of this constituting the actual treatment duration. Route R20 is stated to have a total length of 62.6 km (comprising 37.8 km of salting and 24.8 km of dead running). The material location is treated in the early stages of route R20;
The maintenance compound at West Cowick has a capacity of 6,000 tonnes of rock salt and has a dedicated fleet of four salting vehicles (three front line vehicles and one spare), a loading shovel and a snowblower;

8.56 The Winter Maintenance Plan prepared by WSP is relatively detailed and is considered to describe a highway maintenance system that is capable of meeting the requirements of the TRMM Volume 2 Part 3 (1996), as well as generally following good and recommended UK practice.

Winter Maintenance Operations Undertaken Around The Material Time And Location

8.57 In the preparation of this report, various winter maintenance records have been provided by WSP and Carillion.

8.58 These include a copy of the WSP winter maintenance Standby Rota for the period October 2000 to April 2001. The rota indicates that Paul Fisher was the Duty Standby Officer, and David Hotchkiss the secondary contact, for the WSP Humberside region (West Cowick Sub-Area Office) for the week commencing 27 February 2001.

8.59 In general terms, the period between 22 February 2001 and 4 March 2001 saw a prolonged period of cold weather, characterised by often frosty, icy and snowy conditions.

8.60 The morning summary forecast for the WSP Humberside Region issued at 0621 GMT on 27 February 2001. This stated that 27 February 2001 would be a "mostly cloudy day with occasional light rain and sleet". Of the night 27/28 February 2001, the morning summary stated:

"Overnight more persistent precipitation will spread from the north falling as wet snow or sleet at times. Accumulations of up to 2 cm are possible with temperatures hovering around zero celsius."

8.61 The morning summary also predicted hazards relating to low road surface temperatures, ice and snow.

8.62 The 24-hour text forecast issued for WSP at 1434 GMT on 27 February 2001 referred to the period 1200 GMT on 27 February 2001 to 1200 GMT on 28 February 2001 and predicted ice, snow but no hoar frost with a high level of confidence, and fog with a low level of confidence. The minimum predicted air temperature was -1°C for the period 0000 GMT on 28 February 2001 until 1000 GMT on 28 February 2001. The minimum predicted road surface temperature was -2°C in areas where there would be lying snow, with the prediction being considered valid throughout the 24 hour forecast period.

8.63 The above forecast also included the following text with respect to road state: "A covering of snow expected during today [27 February 2001]. Further snow expected overnight, likely to persist in places tomorrow morning [28 February 2001]"

8.64 The forecast also stated that 10 to 30 mm of snow was to be expected in the WSP Humberside Region during the night of 27/28 February 2001 and the morning of 28 February 2001.

8.65 The forecast concluded with a summary of the weather expected for 27 and 28 February 2001, such that:

27 February 2001 (from 1200 GMT): mainly cloudy with outbreaks of sleet and snow;
Night of 27 / 28 February 2001: cloudy with snow, heavy and persistent at times;
28 February 2001 (until 1200 GMT): rather cloudy with sleet and snow gradually clearing away to the south.

8.66 It appears that an evening update to the above 24 hour forecast was issued at 1810 GMT on 27 February 2001. This specifically stated:

"NO MAJOR CHANGES TO THE MIDDAY FORECAST"

8.67 However, the evening update included an amended concluding summary. The amendment concerns the weather conditions at the time of issue of the evening update and stated:

"Sleet or snow showers have now died away. More persistent snow expected towards midnight."

8.68 A forecast graph for the weather station site on the M62 at High Eggborough, was issued at 1811 GMT on 27 February 2001, which referred to the period 0000 GMT on 27 February 2001 to 1200 GMT on 28 February 2001.

8.69 The copy of this graph provided to TRL includes predicted and actually recorded temperatures during this period. Both the predicted and actual temperatures remained above 0°C for the entire period.

8.70 The forecast text issued for High Eggborough at 1811 GMT on 27 February 2001 referred to the period until 1200 GMT on 28 February 2001. The forecast text accompanied the above forecast graph and predicts a minimum air temperature of -1°C and a predicted minimum road surface temperature of -2 °C. The accompanying text stated that the forecast graph issued at 1811 GMT on 27 February 2001 was based on cloudy skies with rain from midnight, turning to sleet or snow for a time and with road surface temperatures expected to dip close to zero degrees Centigrade during any snow falls. Icy roads were predicted after midnight, also during snow falls. Patchy fog was also predicted.

8.71 With respect to the winter maintenance response of WSP to the above series of forecasts, a typed sheet entitled "Incident M62 Westbound between J35 - J34 Little Heck Railway Bridge", prepared by PG Fisher, Area Maintenance Manager (Humberside) and the Duty Standby Officer for the period 0900 GMT on 27 February 2001 to 0900 GMT on 6 March 2001 has been provided to TRL.

8.72 The sheet provides a winter maintenance chronology for the period from 1200 GMT on 27 February 2001 until 1200 GMT on 28 February 2001.

8.73 The entry for 1645 GMT on 27 February 2001 states that a winter maintenance decision was delayed until the evening forecast update was received, as the hazards previously forecast were not anticipated until after midnight.

8.74 This is consistent with the WSP Winter Maintenance Operations facsimile completed for the Humberside Region at West Cowick depot on 27 February 2001, which stated: "Awaiting evening update. Some action will take place but the timing is unknown as yet".

8.75 It is considered that this was a reasonable response, due to the previous forecasts stating that rain would precede any sleet and snow.

8.76 It appears that Mr Fisher next accessed the ice prediction system at his home, via a laptop computer, at 1900 GMT on 27 February 2001. Mr Fisher indicates that, due to there being no significant change to the afternoon forecast and the fact that rain, sleet and snow were forecast for the period after midnight, a winter maintenance operation was instructed to take place at 2200 GMT on 27 February 2001 utilising a rate of spread of salt of 20 g/m². In addition, staff were instructed to remain on Standby at the depot until further notice.

8.77 The above is consistent with a West Cowick depot log, which contains the following entry for 2200 GMT: "GRITTING PROGRAMME IN OPERATION". The log continues with the following entry for 2350 GMT: "ALL MEN IN DEPOTS AND STANDING BY".

8.78 A winter maintenance record completed by R Walker, the salting vehicle driver on Route 20 (i.e. the route including the material location), has also been provided to TRL. This indicates that salting was successfully undertaken on this route, commencing at 2200 GMT on 27 February 2001.

8.79 It is considered that the decision to salt at 2200 GMT on 27 February 2001 was entirely reasonable, given the relatively uncertain timing and form of any precipitation.

8.80 It appears that Mr Fisher next accessed the ice detection system at 0145 GMT on 28 February 2001, again via a laptop computer at his home. Mr Fisher notes that at this time no changes had been made to the forecast for the High Eggborough outstation site.

8.81 It appears that Mr Fisher then contacted the weather forecast provider (Leeds Weather Centre) and was informed that accumulations of snow would be unlikely in the Humberside Region, but that road surface temperatures may dip close to 0°C.

8.82 Mr Fisher indicates that he then telephoned the security office at West Cowick compound at around 0205 GMT on 28 February 2001 and was informed that rain had fallen since the salting operation at 2200 GMT on 27 February 2001. The above appears consistent with data from the High Eggborough weather station, which indicates that light rain was falling at this location between 0020 GMT and 0120 GMT.

8.83 It appears that the incidence of rainfall resulted in Mr Fisher instructing a further salting operation to take place, again utilising a rate of spread of salt of 20g/m².

8.84 However, there is consistent evidence to the effect that Mr Fisher received a telephone call from West Cowick compound security office between 0210 GMT and 0215 GMT, informing him that rain was falling at Broughton at that time. In response to this information it appears that Mr Fisher instructed that the further salting operation be delayed until the rain had ceased and that, if the delay extended beyond an hour, then the men at the depot should be sent home.

8.85 Mr Fisher received a further call from West Cowick security at around 0240 GMT informing him that heavy rain was by then falling at Cowick and Broughton. The data from the High Eggborough weather station appears broadly consistent with this observation, indicating that light rain was falling at the site of the weather station between 0240 GMT and 0300 GMT. It appears that the information from West Cowick depot prompted Mr Fisher to cancel the further salting operation and an instruction was issued to stand down the men at the depot.

8.86 It is considered that this was a reasonable response to the weather conditions being experienced in the region, given that road surface temperatures were predicted to remain above 0°C during the early hours of 28 February 2001.

8.87 Mr Fisher next received a call from West Cowick depot at between 0630 GMT to 0635 GMT (i.e. some 15 minutes after the accident involving Mr Hart), informing him that sleet and/or snow was falling at that time. This appears to be generally consistent with the High Eggborough weather station data, which indicates that light rain was falling at this location between 0420 GMT and 0720 GMT. It appears that no immediate action was taken in response to the information from West Cowick Depot and that Mr Fisher asked to be informed if snow began to settle.

8.88 The morning summary text issued for the WSP Humberside Area (i.e. including the material location) at 0707 GMT on 28 February 2001, i.e. approximately one hour after the material accident, stated that the weather would be "cloudy with occasional rain and perhaps sleet". The lowest recorded road surface temperature in the region was +1.2°C at Elsham Wold at 0600 GMT, i.e. some 15 minutes prior to the material accident.

8.89 The typed sheet prepared by Mr Fisher indicates that B Wood, a senior supervisor with WSP, reported from the scene of the material accident at 0725 GMT on 28 February 2001, i.e. some 70 minutes after it had occurred. Mr Fisher records that the road conditions were reported as "damp" and that there was "no evidence of snow". This record is considered consistent with the data obtained from the High Eggborough weather station around the material time.

Safety fence provision

Design Of The Bridge Parapet And Safety Fences

9.1 As discussed earlier in this report, the designs for the Little Heck Railway Bridge were formulated between October 1971 and June 1972.

9.2 At the time of design, guidance on parapet provision appeared in the "Ministry of Transport Technical Memorandum on the Design of Highway Bridge Parapets" (BE 5), 1970. BE 5 was in its second reprint in September 1970 after it was first published in January 1967.

9.3 The 1970 revision of BE 5 (and indeed, its previous versions) specified that a P5-type parapet was required for use over all railways. In the specific case of a bridge carrying a motorway over a railway, BE 5 furthers this by stating that:

"205c(i) On bridges carrying a motorway over a railway, vehicle parapets shall comply with all the requirements for a P1 parapet."

9.4 P1 parapets were devised to be capable of containing a 1500 kg vehicle travelling at 120 km/h, impacting at a 20° angle of incidence. BE 5 provides examples of such P1 designs within an Appendix.

9.5 The BE 5 detail for a P5 parapet differs from that of a P1 parapet in that the bottom 600 mm of a P5 parapet should be constructed "so as to prevent stones from being projected onto the railway below by passing vehicles".

9.6 Another difference to note is that BE 5 also stipulates that, for bridges over non-electrified lines (such as at Little Heck at the time of the bridge's design and construction), the minimum height of the parapet above the adjoining paved surface shall be 1.25 metres.

9.7 The as-built parapet drawings for Little Heck Railway Bridge show that the parapet was designed in accordance with the criteria in Paragraphs 9.4 to 9.6 above. As-built drawings also designate the material parapet as being P5-type. Hence, it is felt that, at the time of design, the parapet at the material location met the design requirements of BE 5 (1970).

9.8 With reference to the provision of the safety fences BE 5 (1970) also states that:

"205a(ii) P5 parapets over railways: Where no effective alternative arrangements exist to prevent a vehicle from leaving the bridge approach and falling onto the railway below, a safety fence shall be provided on each approach towards the bridge, as in the cases of Group P1 and P2 parapets."

9.9 With regard to the provision of safety fences in advance of P1 parapets BE 5 (1970) also states:

"201 P1 Parapets, d (i) To prevent direct impact between a vehicle and the end of the vehicle parapet facing the traffic on the nearside, a safety fence shall be provided on each approach towards the bridge. The safety fence shall be at least 30m (100ft) long and shall continue the line of the traffic face of the parapet."

9.10 An as-built drawing from April 1972 (original Drawing Number: 2NE/M62/FP/12/M62-0RLY/1A) shows that an approximately 40 metre length of open box beam safety fence was provided in advance of the parapet at the time of the bridge's construction. This 40 metre length was not all at full height, i.e. it would have included the ramped end down to a buried anchorage. This 40 metre length is termed approximate here, as it has been scaled from the as-built drawings.

9.11 The as-built drawing shows that no flare was originally provided at the anchorage end of the safety fence. Such a flare was not required in BE 5 (1970), but was subsequently specified in the July 1982 revision of that document. It is considered that this may have been one of the factors leading to the apparent replacement of the safety fence during major maintenance work on the westbound carriageway in 1993.

9.12 Drawings issued prior to the maintenance work in 1993 indicate the inclusion of a flare to the end of the safety fence, and it is considered that the drawing is consistent with the safety fence layout currently at the material location.

9.13 A large area of concrete before the anchorage of the safety fence, identified during the post-accident investigation by TRL is also probably a result of the safety fence being replaced during the major maintenance work in 1993. The position of this concrete is consistent with the position of the original anchorage shown in the as-built drawing.

9.14 Safety fence provision at the material location, both at the time of original construction and present at the material time, appear to comply with the pertinent requirements of BE 5 (1970).

9.15 Hence, it is considered that both parapet and safety fence provision at Little Heck Bridge complied with the requirements of the "Ministry of Transport Technical Memorandum on the Design of Highway Bridge Parapets" (BE 5), 1970 at the time of its design and its construction.

9.16 The current standard regarding the layout of safety fences and barriers, "Safety Fences and Barriers", TD 19/85, was published in June 1985. The standard superseded previous publications Memorandum H 9/71 and H 9/73.

9.17 TD 19/85 requires the provision of at least 30 metres of safety fence to protect roadside obstructions. TD 19/85 also reinforces the need for the ends of safety fences to be flared away from oncoming traffic:

"5.1.3 The ends of safety fences facing on-coming traffic shall be ramped down to an anchorage at ground level and flared away from the carriageway by setting back the anchorage behind the line of the fence as detailed in the Specification for Road and Bridge Works, the RM/F series of Standard Drawings and TRRL Drawings"

9.18 Measurements taken at the material location show that a full height length of 33.5 metres is currently provided in advance of the parapet, plus an additional 9.2 metres of ramp down to a concrete terminal, i.e. a total length of 42.7 metres.

9.19 Hence, the requirements of TD 19/85 with respect to the advance length of the safety fence have been satisfied at the material location.

9.20 Technical standard BD 52/93 "The Design of Highway Bridge Parapets" was published in April 1993. The standard details the design of parapets, and supersedes BE 5.

9.21 BD 52/93 states:

"2.21 To prevent direct impact between a vehicle and the end of the vehicle parapet or vehicle/pedestrian parapet facing the traffic on the nearside, a safety fence shall be provided on each approach end of the parapet. A safety fence shall be provided on the departure end where considered necessary. The safety fence shall be at least 30m long and shall continue the line of the traffic face of the parapet."

9.22 As the detail of the safety fence previously outlined in Paragraph 9.18 has shown, the provision at the material location complies with the above requirement.

9.23 The standard (BD 52/93) also states:

"8.5 On bridges over railways with existing or programmed overhead electrification, parapets consisting of a plinth surmounted by metal posts and horizontal rails shall be provided with solid or open infill panels immediately above the top of the plinth up to the full height of the parapet"

9.24 At the time of design, the railway was neither powered by overhead electrification, nor was this planned. As a result, infill panels were not provided on the parapet until the application of aluminium sheets at the material location in May 1987, after notification by British Rail that the railway was planned for electrification.

9.25 When BD 52/93 came into effect in 1993, the parapets at Little Heck Bridge were already equipped with infill panels and therefore met these requirements.

9.26 TRL is informed that the Highways Agency has an ongoing programme of parapet upgrading which includes consideration of this site. This may result in this site being equipped with high containment parapets at some future date.

9.27 However, the provision of a high containment parapet at Little Heck Bridge would not require any greater length of safety fence in advance of it than is currently provided.

9.28 Parapet containment criteria per se are not an issue in relation to the accident involving Mr Hart, as his vehicle did not strike any part of the parapet or safety fence in advance of it. The main issue relating to Mr Hart's accident appears to be the length of safety fence provided. Therefore, it is considered that parapet containment issues are not relevant to these investigations and are not discussed further in this report.

Summary

9.29 In summary, the relevant issue to this report relating to safety fence provision at Little Heck Bridge is the length of safety fence on the nearside verge of the westbound carriageway in advance of the bridge. The measured length on site was found to comply with current national standards and their predecessors.

Performance Criteria For Safety Fences And Parapets

9.30 The controlled testing of safety fences and parapets has been carried out for many years.

9.31 The testing of safety fences has, until recently, been to the guidelines of Series 400 of the Highways Agency's "Specification for Highway Works". This states that safety fences shall be impact tested to the following criteria:

Type of safety fence	Single / Double Sided	Post spacing (m)	Vehicle Mass (kg)	Vehicle Impact Speed (km/h)	Angle of Incidence (degrees)
Open Box Beam (OBB)	Single	2.4	1500 ± 15	113 ± 5	20 ± 1
Open Box Beam (OBB)	Single	1.2	1500 ± 15	113 ± 5	20 ± 1

(Please note that types of safety fence not pertaining to the material location have been omitted)

9.32 The two required OBB tests have been successfully carried out in controlled impact test conditions. In both of the tests, the test vehicle was contained and redirected safely, and the barrier performed to designer's specifications.

9.33 Parapet testing is carried out following the guidelines within BS 6779, Part 3, 1994 "Specification for vehicle containment parapets of combined metal and concrete construction".

Containment Level	Impact Speed	Impact Angle	Total Vehicle Mass	Height of Centre of Gravity	Type of Vehicle
Normal	113km/h	20 ± 1°	1500kg	530mm	Saloon Car
High	64km/h	20 ± 1°	30000kg	1650mm	Four axle rigid HGV

Vehicle Impact Test Criteria, as defined in BS 6779: 3: 1994

9.34 The containment levels contained in BS 6779: Part 3, 1994 can be related to the Parapet Group Designations given in BD 52/93, "The Design of Highway Bridge Parapets", 1993:

P1; P2 (113km/h): Normal level of containment
P5 (excluding footbridges): Normal level of containment
P6: High level of containment

9.35 P5 parapets are designed for use over railways only and differ from P1 and P2 parapets in relation to their design. These differences are outlined in Paragraphs 9.5 and 9.6. The parapet at the material location is of P5 designation, and this is verified by the as-built drawings.

Possible Interaction Between The Material Vehicle And The Safety Fence

9.36 There are two possible ways in which the material vehicle and/or its trailer may have impacted with a longer safety fence at the material site:

Striking the end terminal
Full engagement with the safety fence

9.37 The vehicle involved in the material accident was a Land Rover County. This vehicle has a greater mass than that specified for approval testing in Series 400 of the "Specification for Highway Works" (with the material vehicle's mass being approximately 1800 kg). A vehicle complying with the 1500 kg mass requirement would be a larger saloon motor vehicle such as a Ford Granada or a Vauxhall Omega.

9.38 The Land Rover County has larger wheel dimensions than either of these typical test vehicles and, due to the height of the material vehicle (approximately 2050 mm), the vehicle's centre of gravity will also be higher than that for saloon motor vehicles.

9.39 Due to the differences between the material vehicle and a typical test vehicle, it is difficult to predict what interaction may have occurred if the material vehicle had contacted with a full-height safety fence.

9.40 Past impact tests at TRL have shown that vehicles striking the end concrete terminals of safety fences can, in some cases, become unstable. As the centre of gravity of the Land Rover may be higher than that of a saloon motor vehicle, it is considered that this mechanism may have occurred had the Land Rover struck an end terminal. This could have been to the extent that the vehicle may have rolled onto its side.

9.41 This may or may not have caused injuries to the vehicle occupant. However, it is considered possible that such an impact would have prevented the errant material vehicle from reaching the railway line.

9.42 In order for the entirety of the vehicle to have engaged with a full height section of safety fence, the length of the safety fencing present at the material location would have been required to have been in excess of twice its current length. This can be seen by the material vehicle's tyre tracks shown on Drawing No: 03719/106/2/001, to the rear of this report.

9.43 It is difficult to estimate with any certainty whether a longer safety fence would have successfully contained an impact with the entirety of the material vehicle. As previously stated, the higher centre of gravity of the material vehicle would have increased its propensity to roll in an impact. However, it is considered probable that even partial containment by the safety fence would have directed the errant vehicle away from

Highways Agency

Safe roads, Reliable journeys, Informed travellers

Incident on 28 February 2001 at Little Heck Railway Bridge, Issued August 2002

Highways Report, 30 March 2001

Executive Summary

Introduction

Brief Summary of Incident

Other Investigations

Highway Responsibilities

Scope of TRL Investigation

Methodology of Investigation

Circumstances of the accident

Layout and history of the pertinent section of motorway

Layout and History of Little Heck Bridge and the Safety Fence

Trunk road maintenance standards

Routine Highway Inspections

Routine Maintenance of Highway Structures

Carriageway Maintenance Assessment Surveys

Composition and condition of the road surfacing

General Comments Regarding Skidding Resistance

Measurement of Skidding Resistance and Texture Depth

Sideway-force Coefficient Routine Investigation Machine (SCRIM)

Pavement Friction Tester (PFT)

Texture Depth

Surface Nature of the M62 Westbound Carriageway Around Little Heck Bridge and Visual Inspection

Measurements of Skidding Resistance

Test Methodology

Test Results

Figure 5.2 - PFT Test Results

Comparison of Results with Standards

Table 5.1 - Summary of SCRIM and PFT Measurements

Carriageway profile

Vibra-Line ("Rumble Strip") Provision

Routine highway maintenance

Safety Inspections

Detailed Inspections

Safety Patrols

Debris Lists

Gully Emptying

Hard Shoulder Sweeping

Sideway-Force Coefficient Routine Investigation Machine (SCRIM) Surveys

High-Speed Road Monitor (HRM) Surveys

Deflectograph Surveys

CHART Surveys

Summary

Winter maintenance

Weather and Road Surface Condition

Highway Winter Maintenance Methodology

Winter Maintenance Standards

The System Of Winter Maintenance Operated By The Maintaining Agent

Winter Maintenance Operations Undertaken Around The Material Time And Location

Safety fence provision

Design Of The Bridge Parapet And Safety Fences

Summary

Performance Criteria For Safety Fences And Parapets

Vehicle Impact Test Criteria, as defined in BS 6779: 3: 1994

Possible Interaction Between The Material Vehicle And The Safety Fence