Highways Agency

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.