Overview
It is highly likely that technological innovations in active safety systems for cars will facilitate the study of road safety based on data about specific events. Cars already have systems that can monitor headway and braking, lane position, skidding (electronic stability control), the presence of vehicles in the blind spot (blind sport cameras) and the presence of pedestrians to activate emergency braking. Most cars also have crash data recorders that can store extensive and detailed data about accidents.
The project dealt with research in three main areas: (1) Basic questions and methodological issues, which include accident reporting and accident modelling, the valuation of road safety and the evaluation of road safety measures. (2) Interactions between road users, system elements, and technology, in which the main areas include the high risk faced by young and inexperienced drivers, elderly road users, observation of road user behaviour in natural settings, intelligent transport systems and behavioural adaptation and effects of promoting non-motorised transport. (3) Factors influencing road safety and road safety policy, which comprises public acceptance of safety levels and safety measures, safety management and organisation and cross fertilisation of safety theories between different modes of transport.
Results
The main conclusions of the project can be summarised as follows:
1. Conventional measures of exposure and risk (vehicle kilometres and accident rate per vehicle kilometre) have lost their connection with the foundations of accident research in probability theory. Elementary concepts of accident research should be based on probability theory.
2. It is suggested to re-establish the connection between elementary concepts of accident research and probability theory by re-defining the elementary concepts.
3. It is proposed to define exposure as the occurrence of any event, limited in time and space, that has the potential of generating an accident by making demands on road user cognition.
4. Such events include: encounters (vehicles passing each other in opposite directions); simultaneous arrivals at points where road users enter from potential conflicting directions; turning movements in junctions; braking; lane changing; overtaking; negotiating curves.
5. Each of these elementary types of events can be counted and the total number of events can, in terms of probability theory, be regarded as a sampling frame (population) from which accidents are sampled. Each traffic event has two possible outcomes: accident or no accident.
6. The probability of accident occurrence is simply the number of accidents divided by the number of events having an accident as one of its potential outcomes.
7. The probability of an accident is likely to be negatively related to the number of events. The reason for this is that repeated experience of events can be regarded as a process of learning, in which road user performance becomes more and more reliable.
8. The project has given examples of empirical studies showing a negative relationship between exposure and risk. These studies lend support to the basic hypotheses proposed by the project, but do not represent stringent tests of these hypotheses in terms of the new definitions proposed for exposure and risk.
Policy implications
The project is a base for enhancing the transport safety policy.