Motorway crash barriers

Although there are fewer crashes on motorways per mile travelled than on other roads, when crashes do occur, they are more likely to lead to death because of the high speeds involved. In the UK, 2% of motorway crashes are fatal, compared to 1.4% of all crashes.[2] Motorway crashes are also more likely to result in a pile up and therefore multiple deaths and injuries.

Motorway crash barriers (also known as safety barriers) are designed to prevent vehicles from crossing from one carriageway to the other and to prevent vehicles from impacting or entering roadside hazards. The barriers are also intended to absorb some of the energy from the impact caused by the 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. [3]

Barriers are used to protect road users where there is an identified risk 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. [4]

Performance

The performance of a barrier is made up of two main things: the containment level and the working width of the barrier. The working width is the width of the barrier plus the amount of deflection that occurs when the barrier is impacted. [5] Safety barriers are tested to European Standard EN1317, which is a standardised performance test. A barrier designed for normal containment would be tested with a vehicle of 1.5tons (an average car) hitting the barrier at an angle of 20 degrees at a speed of 70mph. High containment barriers would be tested with a heavy commercial vehicle, up to 38 tons, travelling at 40mph, hitting the barrier at an angle of 20 degrees. [6]

In the UK, there are several different types of barriers available, which perform differently on impact. They can either be flexible, such as a steel wire rope or a steel beam or rigid such as concrete barriers. The Highways Agency has stated that it would be willing to consider other materials or systems if they were to meet ES1317 test standards. To read about different types of barriers click here.

Regulations in the UK

In the UK, the minimum length of barrier that can be installed in advance of a hazard, including at the approach to a bridge over railways, is 30m. However, on motorway and trunk road bridges over railways in the UK, the majority of approaches have safety barriers in excess of 30m in length. [7] 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. [8]

International regulations

In Switzerland, the minimum barrier length is 50m, while in California the minimum length is 15m. The minimum length of barrier to be installed at the approach to a bridge in other countries ranges from 16m in Austria to 98m in New York. [9] Many other countries specify barrier heights measured from the ground to the top of the barrier beams. The specifications range from 0.61m (USA) to 1.0m (Belgium). However, the distance between the top and centre of a barrier beam will depend on the design of the barrier system.

Most countries use barriers with the same strength as the UK for the containment of cars. For the containment of heavier vehicles, other countries use either the same or lower barrier strength than the UK. [10]

To compare UK and international regulations, click here.

Are the regulations enough?

Selby rail crash

On 28 February 2001, tired driver Gary Hart fell asleep at the wheel on the M62. His vehicle left the motorway, went down a bank and on to a train line, causing a passenger train to derail and hit a freight train travelling the other way. 10 people were killed in the crash. [11] Following the Selby crash, concerns were raised about the regulations controlling the length and design of safety barriers over railway bridges and roads. Gary Hart’s vehicle had left the M62 at a very acute angle, well before the start of the crash barriers. The crash prompted a Government report into the design of crash barriers at the ‘road/rail’ interface. It concluded that the Department for Transport guidance on the design of crash barriers, which state that safety barriers should be a minimum of 30m long, had not been breached. [12] To read the full report, click here.

However, the problem with this Government guidance is that there is no recommended length for barriers at different sites. Experts fear that the minimum length of 30 metres (which is necessary for some types of barrier to be able to absorb an impact) is being applied without local aspects, such as curves in the road, being taken into account. Leading civil engineer Professor John Knapton argues that the Highways Agency’s regulations were breached and that more should be done to protect vehicles leaving the road and ending up on railway lines.

“It is absolute nonsense to say that the barrier at Selby was working effectively. Regulations say a barrier has to be positioned anywhere that a vehicle can leave the road and find its way into a dangerous situation. What was clear here is that the driver didn’t steer his car around the curve in the road, and because he went straight on he didn’t hit the barrier and landed on the railway. This breached their regulations.”

Another issue involved with road/ rail barriers is the practical difficulty of devising and implementing the best engineering solution to provide an effective barrier between roads and railways. The appropriate location for a barrier may not be on railway property and the railways have no power to erect barriers outside their property or competence to design barriers from a road safety viewpoint. Highways authorities have the capability and the powers to erect barriers on their side of the boundary, but have no specific duty in law or resources to help them do it. In some cases the best barrier for protecting the railway may not be the best barrier in terms of road safety. [13]

Since the Selby crash, the Department for Transport has developed an “assessment tool”, published in February 2003, for authorities to assess what protection, such as safety barriers, is required at different sites where roads cross rail lines. To read the DfT report ‘Managing the accidental obstruction of the railway by road vehicles’, click here.

Driver killed in flyover plunge

A man died on 17 January 2006 after his car crashed through the barrier of an M8 motorway flyover near Glasgow and landed on a vehicle travelling below. The 38-year-old driver, who was not named, died after his Mitsubishi 4x4 left the eastbound carriageway near Hillington and plunged 50ft onto a Honda Civic. [14]

Barrier selection

The choice of barrier is a very important one; the wrong type of barrier could increase risk for road users. [15] The volume, speed and mix of traffic is used to determine which type of barrier will be used on a particular stretch of road, and decisions are made on a case-by-case basis. [16] At present, the majority of central reservations on major roads in England are installed with flexible steel safety barriers. This type of barrier was chosen for its containment of vehicles and minimum effect on vehicle occupants. [17] However, the Highways Agency has since changed its policy and now recommends the use of concrete barriers on motorway central reserves.

International survey

In 2002 a survey carried out on behalf of the Highways Agency and Britpave examining concrete barrier usage in Europe found that every country that responded used concrete barrier systems. The survey also found that several countries preferred concrete barriers to steel barriers in central reservations, especially where traffic was heavy. Reasons for the preference included safety, low maintenance, less risk of crossover incidents and fewer interventions for repair. [18] To read the full report of the survey click here.

In the UK, crossover incidents account for over 200 motorway crashes and 40 deaths a year. [19]

In January 2005, the Highways Agency issued its new policy (Interim Advice Note 60/05), recommending the use of higher concrete barriers to reduce the risk of crossover incidents on central reservations of motorways with high traffic levels. The policy stated that in most cases, when concrete barriers are struck, they do not need to be repaired and also do not need as much regular maintenance as steel barriers, therefore minimising the exposure and risk to road workers. [20]

The concrete barriers will be introduced gradually and only in new schemes, or motorway-widening schemes. Existing steel barriers will only be changed when they need replacing.

The Highways Agency has highlighted a potential problem that concrete barriers may pose additional risks in certain circumstances where emergency services need to get through the barriers to reach incidents. For this reason the Agency is looking at the requirements for installing moveable gates.

Professor John Knapton has welcomed the introduction of concrete barriers in central reservations and doesn’t believe that they would lead to any additional problems for the emergency services.

“There are already places in all barriers where the emergency services can get through them. You can put access gates in concrete barriers in places where it is very unlikely that there will be a problem. I certainly don’t think it is an issue that should influence the decision of whether to use concrete or steel barriers.”

Professor Knapton believes there are many benefits to using concrete barriers instead of steel ones, including:

They don’t damage the vehicle as much.
They (usually) don’t need any repair after a crash. Currently, repairing barriers will involve closing a road/ lane for repairs to be carried out, with workers being put at risk on the road.
They work equally well with heavier vehicles.
Only one concrete barrier is needed in the central reservation to serve both sides of the road.
There is no headlight dazzle through the barrier.
They need less space as they don’t ‘deform’ like steel barriers.

“Another problem with steel barriers is they are very dangerous for motorcyclists,” Professor Knapton added. “They often decapitate and cut limbs off motorcyclists. I think if steel barriers were to be replaced with concrete ones it would be much, much safer for motorcyclists as, providing they are wearing the right safety equipment, they are going to bounce off the barrier and slide down it.”

Death of motorcyclist

An 18-year-old motorcyclist was killed on 8 October 2005 when he crashed into a steel barrier in Bolton. Police said the teenager, who was not named, crashed into a 1.2m high steel barrier suffering multiple injuries. He died at the scene. [21]

Barriers in other locations

Although the Highways Agency is introducing concrete barriers in all motorway central reservations, the policy applies only to these specific locations and does not apply to verge-side barriers or other routes. Additionally, the policy does not apply to dual carriageways, where there is often no safety barrier at all.

Death on dual carriageway

A Wiltshire coroner and police traffic sergeant called for increased safety measures on a dual carriageway following the death of three men in a crash on the A419 near Swindon. Khurm Sarwar was travelling north on the dual carriageway when his car lost control and veered across the road. The vehicle flipped over after shooting into the air and split in two. Part of the car landed on a Landrover discovery and another car, both travelling southbound. Both occupants of the Landrover, Matthew Williamson and Richard Naylor, were killed, as was Mr Sarwar. During an inquest into the deaths, coroner David Masters accepted police evidence that a crash barrier, dividing the north and southbound lanes of the dual carriageway, instead of the grass verge which was in existence, could have prevented the deaths. [22] To read the full news article, click here.

Professor Knapton believes that in most cases, dual carriageways should be installed with barriers in the same way as motorways. “From an engineering point of view dual carriageways and motorways are often identical. Barriers should certainly be installed on dual carriageway central reservations because this is one of the well known disaster opportunities for vehicles.” However he doesn’t believe concrete barriers would be appropriate for verge-edges, as they would contain vehicles in the road. It will usually be safer to allow a vehicle to leave the road on the verge side, than send it back into the road using a concrete barrier.

Alternatives to crash barriers

Considering the way that roads are built in the UK, there doesn’t seem to be any practical alternative to crash barriers. Motorways and carriageways are usually placed alongside each other, meaning there is no space in between for anything other than a crash barrier. Professor Knapton concludes: “There is simply no room for any alternatives. We put our carriageways very close together. In the USA they keep carriageways about 40ft apart and have a gentle ditch between them. This is a very good idea but we don’t have the space to do it in Britain. I can’t think of anything for British roads that could replace barriers, especially as a lot of our motorways are urban motorways. Bearing the space issue in mind, it does seem to me that using concrete barriers is a much better alternative to steel barriers.”

Conclusions

A 30-metre length of crash barrier is not always long enough, for example on a bend in the road.
The Highways Agency should assess crash barriers on all trunk roads and make crash barriers longer where necessary.
The Highways Agency policy of introducing concrete barriers in central reservations should be implemented practically as a matter of urgency, and not only when a steel barrier comes to the end of its natural life.
If concrete barriers stop crossover incidents and safe lives, then we need to see them on our motorways and dual carriageways straight away.

Sources of further information

Britpave
Department for Transport
Green Flag
Health and Safety Executive (HSE)
Highways Agency
Institute of Civil Engineers
Professor John Knapton

[1] Road Casualties Great Britain 2004 (Department for Transport, 2005)
[2] The Green Flag Report on Safe Driving Part Two, Speed, (Brake and Green Flag, 2004)
[3] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[4] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[5] Highways Agency, Website: www.highways.gov.uk
[6] Highways Agency, Website: www.highways.gov.uk
[7] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[8] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[9] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[10] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[11] Driver Tiredness: an information sheet for fleet managers, Brake Fleet Safety Forum
[12] The Track Obstruction by a Road Vehicle and Subsequent Train Collisions at Great Heck, A Report of the Health and Safety Executive Investigation, (HSE, 2002)
[13] Obstruction of the Railway by Road Vehicles, Report of the Working Group set up by the Health & Safety Commission, (HSE 2002)
[14] Man Dies After M8 Flyover Plunge (BBC News Online, 17 January 2006)
[15] Obstruction of the Railway by Road Vehicles, Report of the Working Group set up by the Health & Safety Commission, (HSE 2002)
[16] Highways Agency, Website: www.highways.gov.uk
[17] To Review the Standards for the Provision of Nearside Safety Fences on Major Roads (Highways Agency, 2002)
[18] Report on European Concrete Barrier Developments, Britpave & the Highways Agency, 2002
[19] Britpave, Website: www.britpave.org.uk
[20] Highways Agency, Website: www.highways.gov.uk
[21] Motorcyclist Killed in Road Crash (BBC News Online, 8 October 2005)
[22] Coroner Calls for Increased Safety Measures on Fatal A419 (BBC Wiltshire News Online, 4 October 2002)