Introduction

Road safety audit is a formal procedure for independent assessment of the accident potential and likely safety performance of a specific design for a road or traffic scheme - whether new construction or an alteration to an existing road. Road safety impact assessment is a formal procedure for independent assessment of the likely effects of proposed road or traffic schemes, or indeed other schemes that have substantial effects on road traffic, upon accident occurrence throughout the road network upon which traffic conditions may be affected by the schemes.

These two procedures enable the skills of road safety engineering and accident analysis to be used for the prevention of accidents on new or modified roads. They thus complement the use of these same skills to reduce the occurrence of accidents

on existing roads by means of local safety schemes, in many cases in the form of low-cost measures

This review aims to describe and illustrate the use of safety audits and safety impact assessment in helping to design and build safe road and traffic schemes, and at the planning stage in choosing which schemes to progress from among a range of possibilities. Generally, roads are designed with a large number of criteria in mind, such as travel time, user comfort and convenience, fuel consumption,

construction costs, environmental impact and objectives of urban or regional planning. Safety is one of the criteria, but is often implicitly assumed to be achieved by adhering to prescribed standards of alignment and layout for each element of the design. These standards are indeed laid down with safety in mind, and some of these include explicit safety checklists (e.g. FGSV, 1988), but experience shows that adherence to them is not sufficient to ensure that a resulting design is free from avoidable hazardous features. Formal safety audit and safety impact assessment procedures ensure that independent expertise is used to make explicit the safety  implications of an entire design and, in doing so, lead to safer designs of both new and modified roads.

Both procedures have strong contributions to make to rational and effective decision-making when considering alternative options, and safety audit is important to the achievement of a safe design for a chosen alternative. The two procedures are complementary - the aim is similar and the difference is in scope and timing.

The scope of safety audit is usually confined to an individual road scheme, which may be a new road or modification to an existing road. The basis for safety audit is the application of safety principles to the design of a new or a modified road section to prevent future accidents occurring or to reduce their severity. The procedure is usually carried out at one or all of five stages in carrying out a scheme: feasibility study, draft design, detailed design, pre-opening and a few months after opening. 

An essential element of the process is that it is carried out independently of the design team. It should be undertaken by a team of people who have experience and up-to-date expertise in road safety engineering and accident investigation. The scope of safety impact assessment is dependent on the scale of the schemes being considered. For small-scale schemes, the impact of change can usually be expected to be confined largely within the scheme itself. In this situation safety impact assessment and safety audit share many procedural characteristics. For larger schemes, the impact on accident occurrence can be expected to be felt over a larger part of the road network. In that case, the impact may be estimated using a scenario technique. By considering different road types, the corresponding values of relevant safety indicators and the forecast traffic volumes, the impact on

accident occurrence can be estimated for different alternatives.

The following two Sections deal in more detail with safety audit and safety impact assessment respectively, presenting information on procedural, methodological and organisational aspects, illustrated by means of specific case studies. Section 4 provides some information about the cost-effectiveness of safety audit as estimated in different countries where this approach has already been in use for some time. Section 5 considers the role of Member States and the European Union in promoting safety audit and safety impact assessment. Direct implementation could play an important role in the further development of the Trans-European Road Network, and implementation in Member States could be promoted in similar ways to that of the now mandatory environmental impact assessment procedures. In the last Section, the main conclusions are set out.

Road safety audits

The aim and nature of a safety audit

In safety audits "The main objective is to ensure that all new highway schemes operate as safely as is practicable. This means that safety should be considered throughout the whole preparation and construction of any project" (IHT, 1996).

More specific aims are:

• to minimise the number and severity of accidents that will occur on the new
• or modified road;
• to avoid the possibility of the scheme giving rise to accidents elsewhere in
• the road network; and
• to enable all kinds of users of the new or modified road to perceive clearly
• how to use it safely.

Whatever the reason for the scheme, a safety audit always begins with a road design. An audit is intended to identify potential road safety problems by looking at the scheme as if through the eyes of the potential users of all kinds, and to make suggestions for solving these problems by applying the principles of road safety engineering (AUSTROADS, 1994; Danish Road Directorate, 1993; IHT, 1996). This means that an audit goes much farther than just assessing whether or not the relevant design standards are properly applied.

By minimising at the design stage the risk of accidents during the lifetime of a road scheme, there is less likelihood of having to take accident remedial measures later, and the whole-life cost of the scheme can be reduced. Road safety audit is an important means for paying explicit attention to road safety during the design of road schemes. This explicit attention should help everyone involved in making decisions regarding changes to road infrastructure to assess the safety implications of the many choices that arise during the design process, and thus increase the road safety awareness of infrastructure planners, designers and authorities.

Organising and carrying out an audit

The process of safety audit as applied to an individual road scheme can be seen as taking place at up to five stages (Wrisberg and Nilsson, 1996), some of which can be combined for smaller schemes:

. The feasibility stage. During this stage, the nature and extent of the scheme are assessed, and the starting points for the actual design are determined, such as route options, the relevant design standards, the relationship of the  scheme to the existing road network, the number and type of intersections, and whether or not any new road is to be open to all kinds of traffic.

. The draft design stage. Horizontal and vertical alignments and junction layout are broadly determined. At the completion of this stage, the design should be well enough established so that, if necessary, decisions can be made about land acquisition.

. The detailed design stage. Layout, signing, marking, lighting, other roadside equipment and landscaping are determined.

. The pre-opening stage. Immediately before the opening, a new or modified road should be driven, cycled and walked. It is advisable to do this under different conditions such as darkness and bad weather.

. Monitoring of the road in use. When a new or improved road has been in operation for a few months, it is possible to assess whether it is being used as intended and whether any adjustments to the design are required in the light of the actual behaviour of the users.

Checklists have been designed for use during each stage of auditing (AUSTROADS, 1994; IHT, 1996). In practice, these checklists have proved very useful as reminders for the auditors, but there is also a risk that they are used too blindly as recipes without sufficient consideration for individual situations. What is required is a combination of judgement, skill and systematic working.

The essence of roa safety audit is that it is carried out by auditors who are independent of the design team, have expertise in both highway design and road safety, and are properly trained and experienced in carrying out audits. This means that not only must they possess sufficient specialised professional knowledge and have the required experience, but they must also possess the communication skills necessary to present audit results constructively and encourage a positive response to them from the design team. Experience has shown that it is preferable to hire a small auditing team rather than a single auditor. The members of an auditing team can jointly offer more skills than an individual, and a team can operate its own system of checks and balances and thus

be less susceptible to its assessments being swayed by personal preferences.

The results of audit should be documented and reported at each stage to the design team and in turn to the client for the scheme. They will usually include recommendations for improvements to the design. There is much to be said for linking a form of certification to the entire auditing process, and having the audit results made public so that citizens, prospective users of the new or modified road,

and other interested parties can make informed contributions to further decision-making. Whether this can be done or not depends greatly on the way in which the decision-making process relating to the scheme is organised. It is therefore impossible to give a generally applicable rule in this regard.

The conduct of safety audits can sometimes lead to tensions between the audit team, the design team and the client for the scheme. What is necessary from the start, therefore, is to create a sufficiently solid, formal basis (whether or not anchored in law) that enables safety audits to be carried out successfully and the recommendations based on the audits to be implemented. There also needs to be commitment to the procedures on the part of the organisations involved. The procedures should include arrangements for dealing with situations in which the design team and the audit team are nevertheless at odds about carrying out the audit recommendations. What is required in these cases is a decision by the client for the scheme, and this may be assisted by some form of arbitration.

Safety audit and existing roads

The development of safety audit for road and traffic schemes, and especially the fifth stage of monitoring the operation of such schemes after they have been open to traffic for some months, raises the question of the role of safety audit or analogous safety checking in respect of existing roads. There is a prima facie case that an independent assessment of conditions on an existing road would be likely to reveal deficiencies indicating scope for cost-effective measures for accident

prevention additional to the accident remedial measures that are routinely identified by investigation of accident occurrence. Yet the task of checking all existing roads is demanding in terms of scarce resources of expertise.

This issue has been investigated in France (Machu, 1996) by means of a pilot study covering nearly 2,000 km of roads ranging from motorways to local roads. The results provide useful indications concerning complementarity between safety checking and accident analysis, the range of deficiencies which it is practicable for the checking to cover, and ways of putting road sections of different kinds into an order of priority for checking during the many years it is likely to take to cover the

whole network