Road Safety Engineering

The road safety engineering (RSE) function has the overarching aim of reducing the risk of collisions on the road network by implementing a range of low-cost improvements.

The RSE function comprises:

• Analysis of personal injury collision data to identify suitable sites for the implementation of cost effective engineering-based improvements to the road network. Sites with collisions involving death and/or serious injury are usually treated with priority.

• Carrying out of road safety audits for every planned and implemented highway scheme that will have an influence on road user behaviour.

• Investigation of each collision that occurs on the road network in which at least one road user dies from injuries sustained in the collision, to determine whether there are any improvements that could be made to prevent further collisions in the same location, or to determine whether the collision forms part of a pattern that should be addressed through other forms of remedial action.

The SERP area

The SERP road network is maintained by three local highways authorities (Essex County Council, Southend-on-Sea Borough Council and Thurrock Council) and the trunk roads and motorways are maintained by Highways England.

The SERP road network covers 5,743 miles[1]. Essex County Council maintains 4,966 miles of road, Southend-on-Sea Borough Council maintains 281 miles of road, Thurrock Council maintains 342 miles of road and Highways England maintains 154 miles of road.

While the principles for collision reduction and prevention are similar across the SERP area, there are some local differences between each highway authority in selection criteria, methodology and initiatives undertaken.

Sites selected for engineering-based highway schemes

With 747 fatal and serious collisions and a further 4,728 slight collisions recorded by Essex Police in the SERP area in 2014, clusters of personal injury collisions are identified. Each cluster is then analysed in detail to determine if there is any pattern in the collisions, such as right turning movements, failure to give-way, excess speed etc. The pattern(s) identified may indicate which aspect of the highway environment one or more road users are failing to cope with at the location. Sometimes the pattern relates to one particular road user group such as elderly drivers, young pedestrians or motorcyclists.

If a pattern in the collisions is identified, road safety engineering specialists determine the sort of measures that could be cost effectively applied to address the pattern. Guidance contained in the RoSPA[2] Road Safety Engineering Manual, together with the experience of local highway and traffic engineers, is used to develop such measures. This approach ensures that limited resources are invested to the best effect to reduce collisions.

Sites are also identified where there has been a pattern of personal injury collisions, recorded by the police, involving vehicles losing control/skidding on a wet or flooded road surface within a three-year period; such a pattern indicates that the condition of the road surface may need further investigation with surface condition data. Sites requiring surface treatment identified via this process are usually included in a future road maintenance programme.

If there are a number of personal injury collisions along a route, these can also be analysed to determine whether there are treatable patterns. For example, whether all the left-hand bends are the scene of one or two collisions, whether people turning right from the major route are experiencing problems, or where a number of junctions along a route are the scene of repeated collisions.

While it is not normal practice to recommend treatment at sites where there are insufficient injury collisions to meet the selection criteria, or there is not an acceptable return on the level of financial investment required, account will be taken of information supplied by members of the public as to where non-injury collisions are occurring on a regular basis. This information, combined with the recorded personal injury data, can help to determine a more complete picture of the issue. In certain cases the issue may be sufficient to attract a low level of funding from the maintaining organisation.

Each identified collision site is monitored on a regular basis in case further collisions, or a change in the collision pattern, occur. Treated sites are monitored to determine whether the predicted return on the financial investment has been achieved and to ensure the treatment has had the desired effect.

Sites having clusters involving similar types of road user, or similar behaviours not suitable for engineering treatment, are targeted through other forms of remedial action such as police enforcement, education or training.

Road Safety Audits

The Road Safety Audit (RSA) process is carried out on each scheme implemented on the highway that will have an influence on road user behaviour, usually following the guidance contained in DMRB[3] HD19/15 or the CIHT Road Safety Audit guidelines. The RSA process is a measure aimed at preventing collisions and is designed to identify features, or particularly the combination of features, within the design of a highway scheme which may increase the risk of collisions after the scheme is implemented.

RSA considers the needs of, and the interaction between, all road user groups. RSAs are carried out at various stages of the design and implementation process, depending on the size and complexity of the scheme. The formal stages of the process are:

  • Preliminary design (Stage 1)
  • Detailed design (Stage 2)
  • Implementation – ideally within 30 days of scheme completion (Stage 3)
  • a) 12 months of collision data available following implementation (Stage 4a)
  • b) 36 months of collision data available following implementation (Stage 4b)

It is often appropriate to combine Stages 1 and 2 for the smaller, less complex highway schemes. 

Fatal collisions

Sites where collisions have occurred, in which at least one road user has died as a result of injuries sustained in the collision, are investigated within 10 working days of the authority being notified. The investigation will be undertaken in conjunction with the police and may well include a visit to the site of the collision to determine whether there are any highway improvements that could be made to prevent further collisions in the same location, or to determine whether the collision forms part of a pattern at the site that should be further addressed through other forms of remedial action such as education, training or police enforcement.

[1] From DfT Road Length Statistics Table RDL0102a

[2] Royal Society for the Prevention of Accidents

[3] Design Manual for Roads and Bridges (DMRB)