Contents

Contents

Annexes

"Major Road" Definitions - Annex 1

Glossary of Terms - Annex 2

Current Standard, TD 19/85 - Annex 3

UK Road and Accident Data - Annex 4

Risk and Probabilities - Annex 5

International Experience - Annex 6

Links

Contents

Working Group Members

To: The Chief Executive and Board of the Highways Agency

Report of The Highways Agency Working Group to Review the Standards for the Provision of Nearside Safety Fences on Major Roads

I am pleased to present the report of the Agency's Working Group that was set up by the Deputy Prime Minister following the tragic accident at Great Heck, near Selby, on 28 February 2001, to review the standard for the provision of nearside safety fences on major roads.

I am grateful to my predecessor, John Kerman, for his work in getting the Group started, and for the time and input from all members of the Group. The efforts made by the Group in achieving so much in a short time is appreciated.

The Group has worked closely with representatives from the Health and Safety Executive who, on behalf of the Health and Safety Commission (HSC), convened a separate Group at the request of the Deputy Prime Minister. They were asked to look at 'the risks arising to railway traffic from incidents where road vehicles have blocked railway lines, and to recommend how those risks can best be controlled'.

Both Working Group reports are required to be presented to the Secretary of State for Transport, Local Government and the Regions in the Autumn.

The Group has examined a considerable amount of English accident data and looked at practice both in this country and abroad. It has generally concluded that incidents involving a road vehicle reaching a railway line (supported by results from the HSC Working Group) are very rare events albeit with tragic consequences.

Our road and rail safety records in this country are among some of the best in the world and our highway standards are continuously improved in such a way that accident figures on major roads are falling. However, we must continue our efforts to reduce accidents and injuries and cannot afford to be complacent. There are no obvious gaps in our standard for safety barriers but there are some areas where improved advice should be considered. A better understanding of what lies behind the standard would aid the dialogue with other parties, such as the rail industry. The Group would like to see any new advice published at the earliest opportunity.

The Group discussed how the UK standard compares with international experience but due to the incomplete nature of the information available, it was not possible to draw firm conclusions. A review of the available information has shown that there is considerable variation in approach. When considering minimum standards the UK compares well with other countries. No data was available on how widely international standards are applied. But an examination of some major roads in England showed that installation is generally above the minimum requirement.

A common approach to risk assessment should be developed by the highway authorities working closely with the rail industry that ensures each others priorities are recognised.

The Group also found that better advice and standards for the provision of safety barriers on minor roads needs to be developed.

Ginny Clarke

Chair of Working Group

November 2001


Highways Agency Working Group Members

Chair

Ginny Clarke, Chief Highway Engineer, Highways Agency

Secretary

Alan Pickett, Director of Civil Engineering, Highways Agency

Members
Others attending
  1. Jeremy Pinington - TRL Limited (Consultant)
  2. Malcolm Macdonald - TRL Limited (Consultant)
  3. Gavin Williams - TRL Limited (Consultant)
Working Group Members

Chapter 1 - Introduction

1.1 The Highways Agency was commissioned by the Deputy Prime Minister to review standards for the provision of nearside safety fences on major roads immediately after a fatal rail crash on the East Coast Main Line. This was caused by a vehicle leaving the M62 motorway at the Little Heck Bridge near Great Heck, Selby, Yorkshire in the early hours of 28 February 2001. A Working Group ('the Group') was formed and was asked to report to the Highways Agency in the Autumn 2001.

1.2 Speaking in the House of Commons on the 12 March, Keith Hill, then Parliamentary Under Secretary of State at the Department for the Environment, Transport and the Regions (now the Department for Transport, Local Government and the Regions (DTLR)) said 'the Deputy Prime Minister has asked the HSC (Health and Safety Commission) to convene and lead a working group that will look at the circumstances of incidents where vehicles have blocked rail lines and whether there are features in common that might have been preventable. In parallel the Highways Agency will be reviewing its standards for safety barriers'.

1.3 In a subsequent statement to the House on 8 May, Keith Hill said that 'the reports of both groups will be presented to the Deputy Prime Minister in the Autumn' (now to the Secretary of State for Transport, Local Government and the Regions).

Terms of Reference

1.4 The Terms of Reference for the Highways Agency Group were set as follows:

"To review the standards for the provision of nearside safety barriers on major roads in the light of recent accidents and make recommendations to the Highways Agency."

1.5 The Group included representatives from highway administrations in England, Scotland, Wales and Northern Ireland, professional institutions and rail operators. The Highways Agency commissioned TRL Limited as consultants to assist the Group with their study.

1.6 The Group first met on 8 June and subsequently on six other occasions to discuss the results from accident data analyses, international experience, research findings and issues papers. They completed their work in November 2001.

The Approach

1.7 The Group agreed to the following as the scope of their work:

The Report

1.8 The report closely follows the deliberations of the Group under the four headings of their agreed approach. The Group first examined data from an analysis of accidents where single vehicles had left the carriageway and had 'struck'/entered roadside hazards causing injury to the vehicle occupant(s). The Group went on to examine these accidents in the knowledge of the current safety barrier standard and its application to major roads in the UK. The Group looked briefly at a comparison with accidents for minor roads. The Group considered analyses of the road accident data that showed the probability of accidents occurring, and in particular where a vehicle ends up on a railway line. The Group also discussed how the UK standard compares with international experience, but due to the incomplete nature of this information, it was not possible to draw firm conclusions. No data was available on how widely international standards are applied or how effective these measures are at reducing the number of injuries arising from road accidents. The Group briefly considered the scale of costs arising from any change in the level of provision of safety barriers.

1.9 The Group has reported on each of the above issues in sequence in the chapters that follow. Summary data are contained in each chapter with more detail where necessary provided in the Annexes. A final chapter draws together the discussion, sets out the Group's conclusions and makes recommendations.

Terminology

1.10 The Group firstly had to agree which roads should be included in the review under the term "major roads". They concluded that "major roads" should be defined as motorways, dual and single carriageway trunk roads and dual carriageway principal roads, thus picking up nationally and regionally strategic roads where the speed limit was likely to be 50 mph or more (see Annex 1).

1.11 It was clear that the review was intended to cover the United Kingdom. The road design and other standards in use on major roads in England, Scotland, Wales and Northern Ireland are jointly developed by the national highway authorities, which in England is the Highways Agency. However, the Group were only able to consider in detail data that covered roads in England and needed to take a view on the application of their findings to major roads in all parts of the UK. This is discussed in Chapter 2.

1.12 The Group also had to agree on a definition of a "safety barrier". They accepted the standard European definition (as given in BS EN 1317 "European Standard for Road Restraint Systems") of a safety barrier as 'a road vehicle restraint system installed alongside, or on the central reserve, of a road'. All safety fences, safety barriers, transitions, crash cushions and barrier terminations are grouped together under the common European definition of 'vehicle restraint systems'. The Group agreed that consideration of the standard for bridge parapets (which are protective fences or walls at the edge of a bridge and provided as part of the construction of a bridge) was outside the scope of the Group.

1.13 Annex 2 contains a glossary of terms used in this report.

Chapter 1 - Introduction

Chapter 2 - UK Experience

2.1 This chapter describes the rationale behind the development of safety barrier advice and the basis of the UK standard. It also briefly describes some recent UK research and its relevance to the development of a new standard.

2.2 This chapter also reports an analysis of accident data where vehicles have left the carriageway on the nearside of English major roads and compares this with accident levels elsewhere in the UK and those on minor roads. The Group was also interested in understanding the extent to which safety barriers are installed on English major roads. Within the allowable timescales it was possible to examine data for sample road lengths and to look specifically at motorway bridges over rail lines.

UK Standards

2.3 The current UK safety barrier standard ("Safety Fences and Barriers" TD 19/85, see Annex 3) is part of the Highways Agency Design Manual for Roads and Bridges (DMRB) and was first issued in 1985. It has been supplemented over time by publication of detailed drawings and advice on the use of new types of barrier, for example Interim Advice Notes 24, 26 and 34 on the use of temporary safety barriers on road works and clearance requirements. Further advice on the use of safety barriers adjacent to bridges is contained in the standard for bridge parapets ("The Design of Highway Bridge Parapets", BD 52/93). Safety barrier requirements also form parts of other standards in the manual. An updated safety barrier standard bringing together all the advice for the UK is being prepared.

2.4 The Highways Agency produces a range of standards and advice contained in its Design Manual for Roads and Bridges. The Manual sets a standard of good practice for the design, assessment and operation of trunk roads (including motorways). It is also applicable, in part, to other roads with similar characteristics. Scotland, Wales and Northern Ireland are co-signatories to the Manual and have in general adopted the Manual for their road networks (the manual contains specific National variations of some of the standards). The DMRB is commended for use by local highway authorities, as the advice is directly applicable to local roads where vehicle speeds are 50mph and over. Where the DMRB is used for minor, lower speed local roads, it is for the local highway authority to decide on the extent to which the documents in the Manual are appropriate.

2.5 The DMRB embodies the collective experience of the Highways Agency, its agents and design organisations over many years, and the other major highway authorities, and as such, represents a guide to best practice. It provides technical requirements and guidance resulting from research and practical experience in the management of the trunk road system in the UK and from overseas. Many of the standards are based on safety needs and they are reviewed and updated as necessary.

2.6 The various parts of the DMRB are the responsibility of the relevant professional or technical specialists within the Highways Agency. They have the responsibility to monitor continuously the performance of the standards by obtaining feedback and keeping abreast of relevant developments in the appropriate technical fields. Standards, Advice Notes and Specifications are reviewed and monitored by commissioning research or other studies as required. When amendments or additions to the DMRB are thought to be appropriate, the Highways Agency convenes a Technical Project Board. This comprises of representatives from Scotland, Wales and Northern Ireland, the Highways Agency and appropriate representatives from industry or local government, who review the proposed amendment or addition, or steer its development. Only if the Technical Project Board is in agreement does the new or amended standard go forward to the National Road Administration Chief Engineers for their approval.

2.7 The DMRB has been prepared for use by appropriately qualified and experienced professionals. It is not a statutory or regulatory document, neither does it cover every requirement in exhaustive detail. Many matters are left to the professional expertise and judgement of users, whilst other matters are covered elsewhere, for example in British and European standards. The British Standards Institution has published a companion document to TD 19/85 as a Published Document PD 6634 Parts 1 to 4 (1999), which describes the different types of vehicle containment systems and their technical development. The technical requirements in the DMRB are to be considered as a desirable minimum and must be adhered to for motorways and trunk roads unless a departure from the requirements is approved (known as a Departure from Standards). The procedure for considering and granting a Departure from Standards involves the designer formally submitting a proposal for departing from requirements with full particulars and a justification to the technical specialists responsible for overseeing the standard. Departures from Standards are only granted in exceptional circumstances where there is little practical alternative except at disproportionately high cost. Designers use their expertise in deciding what additional provision is appropriate at particular locations.

Safety Barrier Development

2.8 The early safety barriers were developed in the USA in the late 1950s and refined through full-scale impact testing, engineering judgement and experience. Many countries began to develop their own safety barriers based on these early systems and applied them to meet their own circumstances. Prime factors influencing the provision of safety barriers included road geometry such as width, profile and horizontal and vertical curvature. Other factors covered traffic volume, speeds and composition.

2.9 The prime requirements for safety barriers are to prevent vehicles from crossing from one carriageway to the other and to prevent errant vehicles (that is, vehicles leaving the carriageway) from impacting with or entering roadside hazards. A safety barrier is intended to absorb some of the energy from the impact caused by an errant vehicle striking it and to redirect the vehicle along the line of the barrier so that it does not turn around, turn over or re-enter the stream of traffic. This is called containment. Safety barriers can be either flexible, such as a steel wire rope or a steel beam, which absorb much of the energy from an impact, or relatively rigid such as concrete barriers, with less absorption of energy. Both types can have the same level of containment but may have very different stiffnesses. Use of standards for safety barriers in the UK result in barriers being provided to protect road users where there is a risk as identified by the standard and where their use can be justified, both in cost and safety benefit terms. Safety barriers are only used where the consequences of a vehicle striking a barrier are considered likely to be less serious than if the vehicle were to continue unrestrained. They cannot offer complete protection from injury to the road user.

2.10 International developments have led to a very wide range of safety barrier designs, which are applied to meet a range of impact considerations by differing vehicles, on a variety of roads. In all instances in the UK barriers have been accepted following validation using full-scale, standardised impact tests, the parameters of which have been determined to meet different national requirements. Full-scale repeatable and reproducible impact tests carried out under strictly controlled conditions continue to be used to validate barrier systems. Two separate impact tests are generally required for this validation. The first test uses a vehicle ranging from a 1500kg saloon car (such as a Ford Granada) to a 30t rigid tanker. This test is mainly used to assess the containment (or 'strength') of the barrier. The second test uses a 900kg vehicle (such as a Ford Fiesta) to assess the reaction of a lighter vehicle impacting the barrier and the severity of any injuries to occupants in the vehicle when it impacts such a barrier.

2.11 In the UK, a study of the types of vehicle in general use led to the adoption of a 1500kg saloon car and an impact speed of 70mph as the most appropriate standard parameters that safety barriers would be expected to control. It was recognised that there was a very wide variety of vehicles in use, but at the same time it was accepted that it would be impractical and uneconomical to use a range of vehicles to validate designs of safety barriers. Following analysis of the dynamics of vehicle trajectory and of accident data, an impact angle of 20 degrees was adopted as being a representative angle of approach. Testing to these parameters (ie a 1500kg vehicle impacting a road restraint system at 70mph, and at 20 degrees) led to the designation of 'normal' containment for a barrier dealing with these parameters. Studies considering heavy goods vehicles led to the adoption of 16t (such as a 2-axle rigid flat bed) and 30t (such as a 4-axle rigid tanker) vehicles for barrier testing.

2.12 The implementation of the European Directive on Construction Products (89/106/EEC, December 1988 as amended by Council Directive 93/68/EEC, July 1993) resulted in the need to harmonize national safety barrier standards across Europe to a common European Standard (EN 1317). This Standard establishes general criteria for testing road restraint systems, with specific performance and test criteria for safety barriers and crash cushions. Four of the six parts of the Standard have been published.

2.13 While it is international practice to validate safety barrier systems by a limited number of successful full-scale impact tests, it is also appreciated that many vehicle impacts with barriers on the live road network lie outside the range of the validation tests. Vehicles will impact with barriers at a variety of speeds, some in excess of the 70mph performance parameter, at a variety of angles of approach and under a variety of levels of driver control. Whilst testing can provide some indication of the likely performance of a safety barrier on the road network, these tests should be regarded as a procedure to select only those systems that meet the minimum performance criteria. Monitoring of in service performance and feedback from accident data, where impacts occur at different angles and speeds, is a recognised means of updating and developing products. As products and circumstances change in the future, so will the validation requirements.

2.14 Having a range of approved safety barrier systems of different performance characteristics leads to the requirement for describing where and to what extent they should be deployed. Taking the most widely used performance parameter as an example (that is to contain a 1500kg saloon car, with minimum effect on the occupants), this indicates the selection of a flexible steel safety barrier with 'normal' containment. These barrier systems are installed on the majority of central reserves on major roads in England, primarily to inhibit vehicles crossing the central reserve. Flexible barriers that meet this level of containment are also installed on the nearside of major roads to prevent contact with defined hazards. An alternative, where there is limited space to allow for the deflection of a flexible barrier, would be to select a rigid concrete barrier. However, there is anecdotal evidence to support the belief that an impact with a rigid barrier will result in more serious consequences for the vehicle occupants than a flexible barrier.

2.15 The objective of installing nearside safety barriers is to reduce the consequences of vehicles leaving the carriageway and encountering a hazard. The UK standard requires normal containment barriers to:

The minimum length of 30m was related to the minimum length at which a safety barrier can be expected to perform most effectively, based on the impact tests.

2.16 It is part of the continuing responsibility of the Highways Agency to monitor the overall need for safety barriers and the degree of containment required taking into account a wide variety of parameters, one of which could be the possibility of an errant heavy goods vehicle. Accident data for vehicles over 3.5 Tonnes in weight indicates that, while they constitute 10% of the total vehicles on major roads, they are involved in only 7% of nearside single vehicle accidents (see Annex 4 Tables A4.3.5 and A4.4.8). Monitoring and accident reports suggest that although the normal level containment safety barrier is designed and tested for 1500kg vehicles, they may also help to contain some heavy goods vehicles. However, if such a vehicle hit the supporting section of a bridge over a major road, then there could be the possibility of a catastrophic structural failure. There are therefore instances where a containment level higher than that for a 1500kg car could be justified for either the nearside or the central reserve. There are a number of barrier systems offering high and very high containment available for use at these particularly vulnerable locations. As the consequences to the occupants of a car striking these barriers is thought likely to be more serious than for impacting normal containment barriers, their use has to be carefully considered and justified.

2.17 Details of the high containment Double Rail Open Box Beam (DROBB) are available in the Highways Agency's Manual of Contract Documents for Highway Works. The very high containment Higher Vertical Concrete Barrier (HVCB) and requirements for the positioning of these barriers are contained in drawings currently issued to designers on a site specific basis by the Highways Agency. The standard requires high containment DROBB barriers, which have been validated for use with vehicles up to 10 tonnes to be used where there is an exceptional hazard to the occupants of vehicles. The very high containment HVCB, which has been validated with vehicles of up to 30 tonnes, can be used at sites where there is an abnormally high risk, such as the risk of an errant HGV causing a catastrophic structural failure.

2.18 The Group discussed the content of the current UK standard and considered that it covered the relevant areas where advice is needed. However, it had been difficult to identify all of the background and reasoning behind the standard, as the document is written for use by highway design practitioners. The Group considered that it would not always be clear to others with an interest in safety what lay behind the current advice. The Group would wish to see more background to the advice to aid the dialogue with third parties and suggested that a more formal framework for regular reviewing and updating standards may be more transparent.

UK Research

2.19 The development of advice on safety barriers to contain cars has taken place over many years, primarily by TRL on behalf of the Highways Agency. TRL, under a similar arrangement, have developed a range of barrier systems to contain heavy goods vehicles.

2.20 The Group was made aware of three topics of UK research ("Accident Study into Safety Fence Provision", TRL 1998) that suggested that changes to the current nearside safety barrier standard should be considered. These topics are described below:

  1. One item defined as a hazard is a lighting column. The frequency of their installation on the nearside affects the likelihood of an impact between a vehicle and the column. Spacing and distance from the edge of the carriageway are factors affecting safety. More specific advice on the protection of lighting columns is required following an analysis of accident data.
  2. At present, safety barriers eventually end by being anchored to the ground at each end, where the barrier angles down from its standard height to ground level. This results in a 'ramp' effect at the end of barriers. Fatal accidents have been reported where cars have hit these ramped ends and then been directed into the hazard that the safety barrier was protecting. Full-scale impact tests have been carried out by TRL to study this phenomenon and the research has led to the development of performance criteria for energy absorbing crash cushions that could be used at the ends of safety barriers. These criteria are now included in the European Standard. A study by TRL of the frequency of barrier endings reported the potential benefit of reducing the number of open gaps between successive safety barriers, where the gap was less than 50m. Accidents where vehicles struck the ends of safety barriers have led to the need for advice on the removal of short gaps in safety barriers.
  3. TRL has studied the application of safety barriers on the nearside of roads. One particular area of interest has been the geometry of embankments at the roadside. This has identified the need to define not only the height but also the gradient of any embankment when justifying the provision of a safety barrier. The ability of an errant vehicle to cross the slope of an embankment is an issue to be taken into account.

The Group considered that the current programme of UK research will lead to improvements to the standard and other advice. The results of such research need to be examined to see how appropriate they are before they are incorporated into new advice. The Group discussed the UK research that had been made available to them and considered that where appropriate it should be included in a revised standard.

Analysis of Accident Data

2.21 The Group wanted initially to be aware of the safety record on UK roads in relation to other countries. UK roads are among some of the safest in the world and compare favourably with other European and developed countries. In terms of fatalities per head of population, England has the lowest number; other parts of the UK reflect well (see Annex 6 Table A6.9). An alternative way of looking at the safety record on UK roads is to look at the number of fatalities per distance travelled (see Annex 6 Table A6.10). Here the UK falls into the middle band with other European countries falling either side.

2.22 The Group asked for a detailed analysis of accident data where single vehicles had left the carriageway on the nearside. These data are only available from accident records (known as STATS 19 forms) completed by the police at the scene of a reported accident where there have been injuries. TRL maintains a database of these records (some 240,000 reports being added each year) and were asked to carry out a variety of analyses to assist the Group in its work. The analyses presented (see Annex 4) are mainly based on English data with summary tables showing broad comparisons with other parts of the UK (see Tables 2.2 and 2.3 below). The STATS 19 reporting system is only applicable for injury accidents and there is currently no mechanism for collecting information relating to damage only accidents.

2.23 The STATS 19 records hold a variety of information about each accident and the resulting injuries. The data are verified by a lengthy process of checking and is made available on an annual basis for Great Britain in the form of statistics published by DTLR. Highway authorities use the data to identify particular accident problems and places on the road network that require a more detailed safety study. The time available to the Group for analysis only allowed for a statistical approach to the data to be taken. Of particular interest to the Group was the breakdown of the data by road type (major, minor, etc) and roadside hazards that caused injuries. Details of individual accidents, for example driving conditions, were not analysed due to time constraints.

2.24 There is evidence that an appreciable proportion of non-fatal injury accidents are not reported to the police (a number of studies have investigated under-reporting by comparing police and hospital statistics). Therefore the accident data collected using STATS 19 forms will under-report the level of injury accidents. The DTLR has analysed this under-reporting and makes comments on it in the introduction to their annual statistics reports (for how this under-reporting may be allowed for, see Annex 5). This development is not relevant for the purposes of comparing numbers of accidents, as it applies to all the accident data, and so no adjustment has been applied to the data for this chapter. An adjustment has been used in Chapter 3 and is essential when estimating risks and the severity of injuries associated with accidents.

2.25 The Group wanted to look at the breakdown of accidents in order to take a view on the adequacy of the safety barrier standard. Before examining the data in detail they asked to look at some broader road statistics about road types and traffic levels that placed their task of looking at major roads into a wider context.

2.26 The Group were made aware of the proportion of the English road network to which their work could be applied. Despite major roads only being 5% of the total road network they carry around 45% of the traffic (see Table 2.1).

Road Type Estimated Percentage Traffic Percentage of road length (1998)
Major Roads:    
Single Carriageway Trunk Roads 6% 1.7%
Dual Carriageway Trunk Roads 10% 1.0%
Motorways 20% 1.0%
Dual Carriageway Principal Roads 9.0% 0.9%
Major Roads total 45% 4.6%
     
Minor Roads 55% 95.4%

Table 2.1 Percentage of Traffic on English Roads (based on Annex 4 Table A4.3.1 and Annex 4 Table A4.3.3)

2.27 The Group wanted to be satisfied that their considerations could be applied to the rest of the UK, even though the Group was considering data covering only English accidents. Table 2.2 shows the lengths of motorway and trunk road and other roads in the UK for comparative purposes while Table 2.3 shows broad levels for nearside accidents on major roads in England, Scotland and Wales.

Click to view Table 2.2

  England Scotland Wales
Single vehicle nearside accidents as a percentage of all accidents 9.25% 13.9% 7.61%
Single vehicle nearside accidents per kilometre 0.42 0.25 0.23

Table 2.3 - Comparison of nearside accident figures on major roads across parts of the UK (from STATS 19 data)
Notes: 1 - road types are not classified exactly the same in all countries and figures are based on the closest comparisons
2 - details for Northern Ireland are not available

2.28 The Group were satisfied from their considerations of the comparison data and on the advice of representatives from Scotland, Wales and Northern Ireland, that recommendations made by the Group based on English accident data would be relevant to the rest of the UK.

2.29 The Group wanted to understand the relationship between the type of road and the quantity of nearside single vehicle accidents. The data indicated that:

Click to enlarge chart

Figure 2.2

 

Figure 2.2 Average number of nearside single vehicle accidents on English roads per year (1990-98) (see Annex 4 Section 4 Table A4.4.1)

The Group discussed these figures and agreed that there are a significant number of single vehicle accidents on the major road network but that they present a more serious problem on minor roads.

2.30 TRL undertook a fuller analysis for the Group and examined the number of injury accidents where particular roadside hazards are struck or entered. The results are in Figure 2.3. As these accidents have all involved injuries they show that hitting objects at the roadside results in injuries to the road user and that there is a range of roadside hazards involved in injury accidents. They further show that hitting a safety barrier or even not hitting a roadside object at all ('hitting nothing') can also result in injury accidents. Hitting nothing could include, for example, leaving the carriageway and overturning down an embankment.

Click to enlarge chart

Figure 2.3

 

Figure 2.3 Average number of nearside single vehicle accidents per year (1990-1998) on major English roads, by roadside hazard (see Annex 4 Section 4 Table A4.4.4)

2.31 TRL have separately investigated the ability of safety fences to contain and redirect vehicles by sampling some typical lengths of English motorway at sites with characteristics that are similar over a length of at least 400m ("Accidents at hard shoulder discontinuities on dual 2-lane and 3-lane motorways", TRL 1998). They classified sites according to the major characteristic of each site, as:

and considered the rates of personal injury accidents at the sample sites. Accident figures for lengths of motorway with and without safety barriers suggested that providing safety barriers does reduce the risk of accident injuries where there are embankments, for example, but raises the risk on a level section. It was found that where sites were level with no safety barrier, there was a lower risk of injury in accidents than sites which were level and where a safety barrier was provided (see Annex 4 Section 5). The figures also show that for single vehicle accidents, accident rates for motorway lengths with safety barrier, level run off, cutting or bridge parapet are fairly similar.

2.32 The results from this TRL work are generally supported by the examination of the trends in reported nearside injury accidents on English major roads over a period of nine years (1990-1998) as shown in Annex 4 Section 4 Table A4.4.18. Injury accidents where vehicles have struck roadside hazards show a general downward trend whilst accidents where safety barriers are struck are increasing. This should not be surprising; over time more safety barrier has been provided on major roads and so the probability of a nearside accident involving a barrier should be expected to increase.

2.33 The Group discussed the results from all the TRL work and considered that increased use of safety barriers could account for the reduction in hazards struck. The Group recognised that barriers themselves can cause injury accidents, as can a vehicle running off the road and not striking a roadside hazard. This tended to suggest that as safety barriers were installed to protect the road user, there should be a clear relationship between the provision of a barrier and the risk associated with the hazard that is being protected (see also paragraph 3.6).

Chapter 2 - UK Experience

Chapter 3 - Assessing Risks

3.1 This chapter considers the risks and consequences associated with nearside accidents and different methods of assessing risk. Having considered the existing standard and an analysis of accident data (see Chapter 2), the Group needed to consider the risk and probability associated with nearside accidents, to inform their considerations about the standard and any need for change. An important part of this consideration are the consequences arising from accidents and their effect on others (third parties), especially rail operators.

Risk and Provision

3.2 A risk is the chance, great or small, that someone will be harmed by a hazard. In the context of the standard, a roadside hazard is any physical obstruction that may, in the event of an errant vehicle leaving the carriageway, result in an accident causing injury to the vehicle occupants. In the case of nearside accidents, the roadside hazards are features along the side of a road, such as lighting columns/lamp posts, bridge supports, telegraph poles, trees, road signs, ditches or other water features, embankments or cuttings, the ends of bridge parapets and any other permanent object. As has already been discussed in Chapter 2 and is shown below, safety barriers on the nearside of roads reduce the chance of an interaction with a hazard but also in themselves carry some risk of injury to the occupants of vehicles striking them. The Group therefore had to consider both the probability or frequency of nearside accidents and the scale of the resulting consequences.

3.3 The estimated total number of vehicles leaving the nearside of English major roads in any one year is about 3400 (see Annex 5 Table A5.2). This figure is based on STATS 19 accident numbers that have been revised upwards to take account of the under-reporting of accidents (see Annex 5 Section 2 for the calculation of the adjustment). The estimated number of single vehicles leaving the nearside of major roads and striking a safety barrier is about 500 vehicles per year, about 15% of the total, while the number likely not to strike a barrier is about 2900 (see Annex 5 Table A5.2). The 15% is reasonably consistent with TRL's observation from a road survey of sections of the M3, M4, A339, and A34 that, despite a wide variation between dual and single carriageways, about 17% of the major road nearside carriageway in England is currently provided with barriers (see Annex 4 Section 1). The estimated number of vehicles striking safety barriers is roughly in proportion to the estimated amount of safety barrier on English major roads.

3.4 The Group were interested in the probability of an accident where an errant vehicle reaches and blocks a railway line. The probability is made up of the combination of a number of single events occurring sequentially. Hence, the probability of a vehicle reaching a railway line would be the combined probability of a vehicle leaving a major road on the nearside, not striking a roadside hazard or safety barrier and travelling a distance to reach a railway line. Figure 3.1 shows a comparison of the estimated number of vehicles per year leaving the nearside of major roads in England, hitting a roadside hazard, hitting nothing, hitting a safety barrier, or reaching a railway line.

Figure 3.1

Figure 3.1 - Comparison of the Estimated Number of Single Vehicles Leaving the Nearside of Major Roads and being involved in a Personal Injury Accident (PIA) taken from Adjusted STATS 19 Data (see Annex 5 Table A5.2)

The analysis in Annex 5 section 3.5 shows that the probability of a road/rail accident of this nature is 0.4 per year. This is equivalent to approximately one vehicle every three years reaching a railway line, from the nearside of an English major road. This does not consider the probability of the vehicle being struck by a train or causing a derailment (as this event is being considered by the HSC Working Group). The Group considered that a vehicle leaving the nearside of a major road and reaching a railway line was an extremely infrequent event, relative to the likelihood of other types of road accidents on major roads.

3.5 The Group were also interested in any differences in the severity of accidents involving safety barriers compared to other roadside hazards. The number of accidents and injuries is recorded by severity in STATS 19 for all accidents involving personal injuries. A measure of the severity of an accident can be estimated by calculating the severity index, which is the number of fatal and serious injuries as a percentage of the total injuries recorded. Assuming the proportion of accidents is of the same order as the recorded number of injuries, then the proportion of single vehicles likely to leave the nearside of an English major road, not strike a barrier and result in a fatal or serious injury accident is about 21% (see Annex 4 Table A4.4.17). The proportion likely to strike a safety barrier but still result in a fatal or serious injury accident is about 18% (see Annex 5).

3.6 The relatively small difference between the severity of injuries arising from accidents not involving nearside safety barriers and accidents involving nearside safety barriers should not be interpreted as meaning the provision of nearside safety barriers is not worthwhile. Since safety barriers are generally provided at sites where the risks are greatest, it is reasonable to expect that without them there would be an increase in the number of serious injuries for the 82% of vehicles that are currently likely to hit barriers without resulting in a fatal or serious injury accident. However, the figures do suggest that providing nearside safety barriers along all major roads would produce only a marginal benefit, if any, in terms of preventing injuries or reducing the severity of injuries. The Group considered that this analysis supported their views reported in Chapter 2 and suggested that the existing policy on major roads of providing safety barriers to protect against particular hazards strikes the right balance (see also paragraph 2.33). They acknowledged that specific hazards of exceptionally high consequences (for example bridges on major roads over railways) may need to be treated as special cases. In such instances a risk assessment may be required to identify the locations or roadside hazards that may need particular attention.

Risk Assessment

3.7 Risk assessment requires possible events to be broken down into logical groups, for each of which the risks can be identified. The possible hazards are examined and the associated risks (which may relate to safety, time, costs and so on) are evaluated. A risk assessment at a specific site should identify and record what the problem is, the potential risks at the site and whether the risks have been considered and eliminated or, as far as is practical, mitigated. If that risk assessment forms part of a programme of assessments that is identifying mitigating work, then the assessment should also provide a means of prioritising that work.

3.8 The Group were unable to identify any explicit risk assessment in use for determining the provision of nearside safety barriers on major roads in the UK. The existing standard establishes a set of criteria under which safety barriers should be provided. In effect, a risk assessment has already taken place during the development and establishment of the standard, as the priorities for hazard protection in it are based on research and analyses of accident data. The standard gives minimum requirements for the provision of barriers, however there will be cases where additional provision is required. The designers are expected to use their experience in identifying locations where more than the minimum requirements are to be provided. Site-specific risk assessment could be used to determine the level of provision in such cases but at present there is no recognised methodology. Although the Group found no evidence that the standard as such had led to unsafe practices, they considered that a formal risk assessment method for the provision of safety barriers would be helpful to all those involved in making decisions about the provision of nearside safety barriers.

3.9 The Group were also unable to identify any explicit risk assessment in use to address all the risks at sites where road bridges cross railways. The UK highway authorities do currently use risk assessment to prioritise programmes of upgrading bridge parapets across their networks. The assessment model looks at the potential hazards associated with a site and then applies a predetermined expected frequency of occurrence and consequences. In broad terms it attempts to predict how hazardous a site is.

3.10 The rail industry uses risk assessment to help make safety decisions, based on historic accident information. There is a computer-based Safety Risk Model that provides the causes and consequences of potential accidents and shows how risk can be reduced, in terms of the costs of avoiding fatalities and injuries on the railway. The Group considered that a method of risk assessment that is common to both the road and rail industry, that would identify and prioritise the risks at sites where there is the potential for conflict between major roads and railways would be helpful to all parties. The Group acknowledged that, for a method to be acceptable to all parties, it would have to include a means of comparison of these risks with other risks on the road and rail networks.

3.11 The Group recognised that a risk assessment approach for minor local authority roads would also be beneficial, although it was not part of the remit of the Group. A methodology that is currently being developed for local authority roads was briefly reviewed. The Group discussed the principles of this draft framework and suggested that the DTLR should ensure that necessary further work by the appropriate bodies be undertaken to produce a risk assessment methodology that could be implemented for local authority roads. It would be useful if this assessment methodology could be compatible with risk assessment methodologies for major roads and the Group considered that this may provide a starting point for work on major roads.

Consequences

3.12 When an accident occurs there can be a range of consequences, related to the severity of the accident and other factors such as who and what is affected. The Group were interested in comparisons between the consequences of accidents involving roadside hazards and accidents involving third party property or equipment (such as the railways), which might be expected to be further away from a road than identified roadside hazards. The Group considered a comparison of the economic value of risk for various theoretical nearside accident scenarios on English major roads. The scenarios could be described as:

Annex 5 demonstrates how the economic risk value of each scenario was calculated as the product of the probability and the estimated value of the consequence. The scenarios used similar injury numbers, unit rates and estimated total consequential costs of disruption and other losses of typical events to produce an economic value of the risks.

3.13 The analysis suggests that in numerical terms, the economic value of the consequences arising from a roadside hazard accident are significantly less than the economic value of the consequences arising from a major road/rail accident. However, these are more than balanced by the probability of a roadside hazard accident occurring being that much greater than a major road/rail accident. The comparison of the economic risk values is shown in Figure 3.2.

Figure 3.2

Figure 3.2: Comparison of the Economic Risk Values for a Typical Road Hazard, Typical Off Road or Third Party Hazards and Railway Lines (see Annex 5 Section 5).

3.14 The comparison suggests that unprotected roadside hazards alongside English major roads have a greater economic risk value than road/rail hazards where a road vehicle may reach a railway line, despite the possible disproportionately high consequences of such an event.

3.15 The Group also discussed the implications of the rail industry's approach towards the causes of major accidents (that is, accidents involving multiple passenger fatalities). The rail industry takes all reasonable practicable measures towards unsafe acts and conditions, which are in the direct control of the rail industry, to reduce the chances of such accidents occurring. They have a long term goal to reduce injuries from train accidents near to zero by 2009.

3.16 All forms of transport involve a degree of risk. As with other modes of transport and other industries, the most effective ways of increasing railway safety involve driving down the number of events and procedures that can represent a serious risk.

3.17 Highway authorities, also take all reasonable measures to reduce accidents, but are in a different position because they exercise less control over the actions of drivers on their network. It is therefore recognised that the scope to reduce risk is different between road and rail. The Group recognised this position but considered that the rail industry's approach should be taken into account when deciding on the level of highway protection at road over rail locations.

Chapter 3 - Assessing Risks

Chapter 4 - A Comparison With Some International Practice

4.1 The Group were asked to look at the relevant international experience and whether there were any features that would be worth considering for introduction into UK advice. TRL were asked to investigate the practice in a selection of countries, where transport infrastructure is similar to the UK and report on some of the main features in their standards. Historical information was also collected from library sources.

4.2 This chapter considers the international practice and looks at how it compares with the application of the standard on major roads in the UK. The data on barrier provision collected by TRL for the M3, M4, A34 and A339 has been used to estimate the level to which the standard is implemented on the road network. Additionally, data on the lengths of barriers at trunk road and motorway bridges over rail lines has been collected by the Highways Agency to aid the comparison. The Group had already considered the overall safety record on UK roads in relation to other countries (see paragraph 2.21).

International Standards

4.3 In approaching a range of countries TRL asked for information on the following:

  1. Current Standards for safety barrier systems.
  2. Documents that control or advise on where, if at all, particular safety systems should be installed.
  3. Documents that relate to the specific provision of safety systems where roads pass over rail tracks.

The response was varied with returns being received from a dozen or so countries. No country provided details of how widely their standards are applied or the effectiveness of their measures at reducing the number of injuries arising from road accidents.

4.4 International experience shows that other countries consider a variety of factors (some of which are combined) in order to determine not only the length of safety barrier, but also the containment capability of the barrier and the overall layout of the barrier. These factors include traffic speed and density, the geometry of the site, the distance of the hazard from the main carriageway and the physical dimensions of the hazard. The UK standard also considers such factors and provides advice on the basis of the minimum acceptable design with general advice on where additional provision should be considered.

4.5 International experience has shown that there are a number of differences between the methodologies surrounding the installation of safety barriers in the UK and those used in other countries. However, it is not currently known whether the provision of safety barriers 'in the field' is the same as that specified in their standards. For example, standards will generally apply to new works and hence existing roads may not necessarily be retrospectively upgraded to the requirements of new standards. It is also unclear how effective these alternative approaches to safety barrier installation are at reducing injury rates. Accident figures from other countries, where sufficient detail was available, would give a guide to this, but time restraints have not allowed the Group to consider this.

4.6 TRL assessed the international information they received and produced comparisons against the areas connected with the provision of barriers that the Group were interested in, broadly being the length and strength of barriers, the choice of barrier type and risk assessment methods. A summary of the detailed comparisons is at Annex 6. It is important to note that not all countries provided the same type of information, however where information has been provided, it has been included, where relevant. The sections below therefore are not comprehensive.

Barrier Length

4.7 In the UK the minimum length of barrier to be installed in advance of any hazard is 30m. This stands towards the top of the range of countries that use a defined minimum length. Switzerland define a minimum length of 50m, while the shortest minimum length comes from California at 15m (see Annex 6 Table A6.1).

4.8 The road survey of sections of the M3, M4, A339 and A34 (totalling approximately 160 miles (257km) in length), has found that all of the 379 safety barrier lengths present on the nearside, and at hazards, were at least 40m. These lengths included twenty on the approach to bridges over a live railway line. Lengths of up to 2300m were found in-situ on both the M3 and M4; a full table of the lengths is in Annex 4 Section 1. This highlights the fact that within the UK there are notable differences between the minimum provision quoted in standards and the lengths that are actually installed 'in the field'.

4.9 The Group were interested in the length of safety barriers provided at rail bridges internationally. The UK specifies 30m as the minimum length of barrier to be installed at the approach to a bridge over railways. Other minimum lengths range from 16m in Austria to 98m in New York (see Table A6.2 in Annex 6). In Germany two parallel rows of safety barriers (of different lengths and different levels of containment) are recommended on bridge approaches.

4.10 Other countries specify a method of calculating the length of safety barriers, including those at bridge approaches, although a minimum may also be specified. The approach is varied but is generally based on the anticipated angle of approach of a vehicle. The application of such methods to UK major roads could produce bridge approach lengths in a range from about 105m (using Australia's method of calculation) to 140m (using Canada and New York's method of calculation).

4.11 The Group also considered an analysis of the lengths of safety barrier at the approaches to motorway and trunk road bridges over rail lines in England, provided by the Highways Agency. This showed that the majority of approaches to rail bridges have safety barriers installed in excess of 30m in length. The specified minimum length of 30m at bridge approaches is provided to protect the end of the bridge parapet. Additional lengths of barrier ought to be provided according to the hazard that the bridge passes over or to the roadside conditions in advance of the bridge approach, leading to total lengths well in excess of 30m. There are locations where the barrier length is shorter than the 30m standard due to local physical conditions (such as requirements for access) and at these locations a formal departure from the standard will have been approved (see Chapter 2 for an explanation of Departures from Standard). Table 4.1 below provides a breakdown of the lengths of safety barrier found on a large sample of sections of the motorway and trunk road network in advance of rail bridges (see Annex 4 Section 2).

Range of length of Safety Barrier Number of Railway Bridge Approaches
<30m 124
30-40m 115 } - 461
41-50m 34
51-100m 83
100+m 128
Continuous 101

Table 4.1 Lengths of Safety Barriers on approaches to rail bridges on English Motorway and Trunk Roads (see Annex 4 Section 2 Table A4.2.1).

4.12 In the USA regulations indicate that the length of safety fence may be shortened by the introduction of a long flare, angled away from the main carriageway. The regulations state that "this enables a hazard to be protected, without the costly application of long sections of safety fence. This method is particularly effective at reducing the probability of a vehicle entering a hazardous area after leaving the carriageway at a narrow angle. It may have adverse consequences for the vehicle occupant(s)".

Barrier Height

4.13 In the UK most types of metal safety barrier are required to be 0.61m high, measured from the ground to the centre of the barrier beams. Many other countries specify barrier heights measured from the ground to the top of the barrier beams. These range from 0.61m (USA lower limit) to 1.0m (Belgium), although the distance between the top and centre of a barrier beam will depend on the design of the barrier system involved. A comparison between different countries is in Annex 6 Table A6.3.

Selection of Barrier Type

4.14 In the UK there are several approved barrier types available for use, which have different performance characteristics, whilst still meeting the required criteria. For example, rigid concrete barriers, flexible wire rope and semi-rigid steel safety fences perform in different ways during impact and may have different overall levels of containment, in addition to different installation and maintenance costs. The information collected during testing, especially that relating to the barrier's performance during impact, can then be used to determine which type of safety barrier, and in what configuration, is most suitable for a particular application.

4.15 UK standards define the containment levels required in particular locations, but do not specify particular safety barrier products. As a result, they identify some locations where a greater level of protection for the road user may be required. Other countries select the type of barrier to be used according to an assessment of various criteria, such as traffic conditions, distance of the hazard from the carriageway, field experience and so on. Australia, New Zealand, Canada and USA, for example, have an established set of criteria that cover barrier performance, barrier deflection, site conditions, cost and so on, in taking decisions about what type of barrier to use.

Barrier Strength

4.16 A comparison between the barrier containment (strength) used in different countries is in Annex 6, Table A6.4. The comparison shows that most countries use barriers with the same strength as the UK for the containment of cars ('normal' containment). For the containment of heavier vehicles ('high' containment), other countries use either the same or a lower barrier strength than the UK.

Risk Assessment

4.17 In the UK there are specific conditions under which safety barriers are installed on the nearside of major roads. Several other countries use different methods ranging from the individual assessment of each case to an assessment of the hazard using standard data.

4.18 The degree of risk assessment varies between countries (see Table A6.6 of Annex 6). France, for example, uses severity indices and looks at the probability of leaving the carriageway, the consequences for the vehicle occupants and the consequences to third parties. Australia has a methodology that uses a flowchart which defines the problem (in terms of the hazard, and an associated severity index, traffic flows and speeds and roadside geometry), determines the risk (using probabilities) and then develops options. Canada and the USA produce lists of roadside hazards that normally require protection. They then consider whether the consequences of a vehicle striking the hazard or running off the road are more serious than the consequences of a vehicle hitting a barrier, and then apply cost benefit analysis.

Road Geometry

4.19 TRL's comparisons showed that most countries have criteria for determining the provision of barriers on embankments using embankment height, the gradient of the embankment slope, or a combination of the two (see Table A6.7 in Annex 6). In the UK, it is only the first of these criterion that is used. A number of countries, including the UK, also apply criteria for providing barriers when there is a curve in the road of less than a certain radius.

Use of Clear Zones

4.20 A clear zone is a zone from the edge of the carriageway, which is traversable and obstacle free. The aim of a clear zone is to allow errant vehicles to be brought under control and appropriate action taken. This zone varies widely between countries, due in part to the available space and the approach taken to the geometric design of the road.

4.21 TRL's comparisons (see Annex 6 Table A6.8) determined that there was a range of clear zones internationally, from 2.5m in Hungary to 13m in the Netherlands, with some countries defining greater clear zones for motorways than for other high speed roads. The UK defines a clear zone of 4.5m for motorways only.

4.22 Australia relies on a graphical method for determining a clear zone. There, the width of the clear zone is dependent upon the gradient of the embankment at the side of the road, and the average daily flow of traffic. Canada also uses an approach based on the gradient of the embankment.

Chapter 4 - A Comparison With Some International Practice

Chapter 5 - Cost of Change in Provision

5.1 The Working Group considered the cost and practicality of the implementation of any change in the provision of safety barriers. For example, the introduction of a formal risk assessment methodology (as discussed in Chapter 3) might result in a different level of provision at a specific site than that provided by the existing standard. The Group decided to look at typical costs of additional provision of safety barriers.

5.2 The cost of work on existing major roads is highly dependent on the amount of traffic management that is necessary to safely carry out the work. For example, additional safety barrier provision on a motorway may involve closing the nearside lane while the work is carried out. Additional safety barrier provision on a minor local road may require traffic signals or even traffic diversions. This traffic management can be the largest element of the total cost and can vary greatly from site to site. A typical unit cost for the provision of an additional one metre of nearside safety barrier as part of the construction of a new motorway or trunk road bridge, say, could be about #pound;50, which is small in comparison to the cost of providing the new bridge. However, a typical unit cost for providing an additional one metre of nearside safety barrier on an existing motorway or trunk road, where specific traffic management will be needed, could be about #pound;250 (excluding any cost of delay to traffic as a result of the work).

5.3 The difference between these two unit costs is largely the result of the difference in approaches that would be required. Each additional length of safety barrier provided at a new bridge would be installed to best fit with the construction of the bridge and would be done as part of the overall work being carried out. Installation of additional lengths of safety barrier on the existing motorways and trunk roads would probably have to be carried out as discrete elements of work. This would not only require separate traffic management (lane closures, traffic signals, traffic diversions) but would also have to include the removal of existing barrier anchorages and dealing with any public utility apparatus. There is an additional risk arising from the work required to install additional barriers, to both the road user and the workforce carrying out the installation. These risks would need to be included in any risk assessment.

5.4 Having identified the need for the adoption of a more robust risk assessment, which will identify both the costs and benefits of barrier provision at particular locations, the Group was not in a position to quantify the extent of barrier that might be required or its overall cost. However, from the unit costs, it was clear that costs from any changes to the level of provision of safety barrier arising from their recommendations are likely to be reasonably low.

5.5 Generally, revised standards only apply to roads that are built after the date of introduction of that standard; they are not generally applied retrospectively. In this particular case the Group considered that their recommendations should apply to work carried out on the existing road network as well as to new works.

Chapter 5 - Cost of Change in Provision

Chapter 6 - Conclusions and Recommendations

6.1 This chapter draws together the discussion and conclusions reached by the Group into a series of recommendations, many of which require further work to be undertaken or are suggestions for more study and research.

Conclusions

6.2 The Group has reviewed the current standard under the four headings that set the scope of its work in Paragraph 1.7 namely:

A comprehensive analysis of nearside single vehicle accidents on English roads has confirmed the importance of preventing errant vehicles from striking hazards along the edges of roads. Vehicle impacts with obstructions such as trees, posts, and telegraph poles are most likely to result in fatal or serious injury to the vehicle occupants and should have a high priority for protection by a safety barrier. Whilst there are a significant number of such accidents on the major road network, there is a more serious problem to address on the rest of the UK road network. Using accident data and recent UK research, the Group reviewed the performance of the current safety barrier standard. The Group found that the evidence demonstrates that safety barriers can themselves present a hazard to errant vehicles but the Group concluded strongly that, on the whole, the standard provides the right level of protection. They also found no overwhelming evidence to suggest that there is a significant problem with Heavy Goods Vehicles leaving major roads on the nearside, which lead the Group to conclude that there should be no general increase in the level of containment. The Group also supported the approach in the current standard where selected hazards are identified for protection, at an appropriate level of containment.

The accident data was further analysed for the Group to estimate the likelihood of accidents occurring and to compare the effect of interacting with different hazards and the associated risks and consequences. The Group concluded from this that the current policy on protection strikes the right balance and that accidents involving vehicles leaving major roads and reaching railway lines are extremely infrequent events. They acknowledged, however, that such events could, in exceptional circumstances, have very serious consequences for the rail industry. The Group accepted that implicit in the current standard is an assessment of which hazards require protection and that this is a form of risk assessment. In addition, experienced and qualified highway designers use the standard as a minimum provision but evidence shows that the provision on major roads generally exceeds the minimum requirements. The Group concluded that there is no evidence to support a step change in the current policy for safety barrier provision on either major roads or minor roads. They accepted that highway authorities operate procedures that are as safe as is possible, however, the approach to safety in the rail industry is rightly different and this is not always sufficiently taken into account in current roads practice. The railway safety approach is risk based where a protocol of comprehensive risk assessments is adopted and used. The Group concluded that whilst the evidence suggests that road/rail incidents are extremely infrequent for major roads, a more formal and transparent framework for risk assessment and an agreed protocol, common to both rail and road authorities, could help to better manage these risks.

A number of standards relating to safety barrier practices were collected from other countries. Within the time available it was not possible for the Group to study the effectiveness of these standards, or the result of applying the various standards to UK major roads. In general, the Group concluded that the current UK standard compares well with those from other countries where a minimum standard is specified. It was recognised that most of the international standards are aimed primarily at new road building and time did not allow the Group to determine to what extent these practices are applied retrospectively to the existing road networks. The Group concluded that there might be an advantage in understanding some other countries' practices and methods to determine whether they could be beneficial to the UK in determining the extent and location of safety barriers and also in adopting a more analytical risk assessment approach. Any such approach would require more comprehensive advice to be provided and for it to be better explained in the standard. The Group recognised that there is currently a lack of advice on risk assessment procedures and concluded that this should be provided.

Chapter 5 of the Report contains the results of the Group's consideration of costs for installing a limited additional length of safety barrier where this could be justified, following a detailed risk assessment. The Group concluded that there is no evidence to support a general increase in protection measures on the UK's major roads, but that there is a lack of advice for local authorities to use on minor roads. They acknowledged that the analysis of English accident data shows that the risks to vehicle occupants in accidents involving many unprotected roadside hazards are greater than those from a vehicle reaching a railway line. The Group concluded that the unit cost of additional lengths of safety barrier is small for new works but is considerably greater for existing sites, which would require traffic management. However, they also concluded that the overall costs of any changes in provision would be likely to be reasonably low.

6.3 The overriding conclusions from the Group are:

Recommendations

6.4 The Group having considered the conclusions make the following recommendations, grouped similarly to their conclusions.

6.5 The current standard has been shown to have the right balance for major roads and to cover the appropriate topics. The analysis of accident data has shown that priorities for protection of road users from nearside hazards are appropriate. The standard compares well with those from other countries in most respects but the form of any review and background to the advice is not clear. The Group recommends that:

  1. The latest UK research and best practice from international experience is incorporated at the earliest opportunity into standards. (see paragraphs 2.20 and 4.7 - 4.22)
  2. Additional research is targeted at issues where either accident data or international experience identifies potential shortcomings. In particular, research should be undertaken into understanding more about how and where errant vehicles travel after leaving the carriageway. (see paragraphs 2.20, 2.21 - 2.33 and 4.7 - 4.22)
  3. The Highways Agency introduces a clearer and more open procedure for updating the standard relating to safety barriers. (see paragraphs 2.6, 2.7 and 2.18)

6.6 Accidents involving nearside hazards are a greater problem on minor roads where there is little advice available. The Group recommends that:

  1. DTLR take the lead in bringing together the interested parties to prepare advice on appropriate mitigation measures for application on minor roads crossing rail lines. (see paragraphs 2.4, 2.29 and 3.11)

6.7 There is a lack of advice on risk assessment and there is a lack of clarity on where the responsibility lies between road and rail authorities for preventing errant vehicles accessing railway lines. It is clear that this must be overcome in partnership between the interested parties. The Group recommends that:

  1. Risk assessments be further developed for the provision of safety barriers, including additional and/or alternative protection or mitigation measures to take account of local circumstances. (see paragraph 3.8)
  2. A common risk assessment framework for road/rail interfaces be prepared and used in order to identify high risk sites and prioritise work programmes. (see paragraphs 3.9, 3.10 and 3.11)
  3. The risk assessment methodology recognise the needs of both road and rail as separate authorities and their need to address wider safety interests. (see paragraph 3.10)

6.8 During the work of the Group it was found that the quality of accident data and the under-reporting of accidents needed to be addressed. Due to the lack of time the Group were unable to fully investigate the level of application of international standards and the relevant safety records. The Group recommends that:

  1. The Highways Agency enhance the collection of accident data including reporting links matching barrier repairs with non injury accidents. Other national highway authorities are recommended to consider similar action. (see paragraphs 2.13, 2.14, 2.16, 2.22 and 2.23)
  2. Data are collected on the implementation and effectiveness of barriers abroad. (see paragraph 4.5)

6.9 The Group has concluded that for major roads the analysis of the accident data suggests that there are no major shortcomings in the safety barrier standard or its application. As such, the data does not support the wider use of safety barriers everywhere on the road network. Further consideration and specific advice is required at certain locations, such as at road bridges over railways, where there could be exceptional, disproportionate consequences. The Group recommends that:

  1. The standard is reviewed to take account of the Group's recommendations and the thinking behind the standard made clearer. (see paragraph 2.3 and 2.18)
  2. Additional measures that may be required from application of the amended standard be implemented and should apply to works on the existing road network as well as to new works. (see paragraph 5.5)

6.10 The Group recommends that:

  1. Action to implement the recommendations is undertaken within twelve months and the Highways Agency report on progress at that time.
Chapter 6 - Conclusions and Recommendations

Document References

"Safety Fences and Barriers",
TD 19/85; June 1985; Design Manual for Roads and Bridges, The Highways Agency/The Scottish Office/The Welsh Office/The Department of the Environment for Northern Ireland

"Use of Temporary Safety Barriers at Road Works",
Interim Advice Note 24; December 1998; Highways Agency

"Safety Fences and Barriers",
Interim Advice Note 26; February 1999; Highways Agency

"Use of 'Varioguard' Temporary Safety Barriers at Road Works",
Interim Advice Note 34; January 2001; Highways Agency

"The Design of Highway Bridge Parapets",
BD 52/93; April 1993; Design Manual for Roads and Bridges, The Highways Agency/The Scottish Office/The Welsh Office/The Department of the Environment for Northern Ireland

"European Standard for Road Restraint Systems"
BS EN 1317-1 Road Restraint Systems - Part 1: Terminology and general criteria for test methods.
BS EN 1317-2 Road Restraint Systems - Part 2: Performance classes, impact test acceptance criteria and test methods for safety barriers
BS EN 1317-3 Road Restraint Systems - Part 3: Crash cushions - performance classes, impact test acceptance criteria and test methods
pr EN 1317-4 Road Restraint Systems - Part 4: Performance classes, impact test acceptance criteria and test methods of terminals and transitions of safety barriers
pr EN 1317-5 Road Restraint Systems - Part 5: Durability and evaluation of conformity
pr EN 1317-6 Road Restraint Systems - Part 6: Pedestrian restraint systems. Pedestrian parapet

"Accident study into safety fence provision: final report";
1998; Janet V Kennedy, TRL

"Accidents at hard shoulder discontinuities on dual 2-lane and 3-lane motorways";
1998; J P Fletcher and I Summersgill, TRL

Document References