Evaluation of the Safety Benefits of Passive And/or On-board Active Safety Applications with Mass Accident Data-bases

One of the main objectives of the European TRACE project (Traffic Accident Causation in Europe, January 2006 – June 2008) was the development of methodology for the evaluation of the safety benefit of existing on-board safety applications in passenger cars with the use of mass accident data-bases only. The challenge was to evaluate passive safety applications as well as active applications and especially combinations of the two within a single investigation. In order to do so the well known concept of odds-ratio has been generalized for jointly evaluating injury mitigating effectiveness as well as accident avoiding effectiveness at once. This paper describes statistical sound methodology that is able to evaluate the safety benefit of either a single on-board safety function or the additional gain of specific safety feature(s) (i.e. a selection of various passive safety functions and active safety functions), given that some other safety applications already are on board. In particular, the method allows for evaluation of accident avoiding effectiveness as well as injury mitigating effectiveness. Hence, it can be applied for joint evaluations of passive and on-board active safety applications. The focus of the paper lies on the presentation of a ready-to-apply methodology, including detailed examples as well as a discussion on its advantages and its limitations. EFFECTIVENESS OF SINGLE SAFETY FUNCTIONS For measuring the effectiveness of a safety function it is of critical importance to distinguish between different possible types of effects. In general there are at least four different types of safety function effects. These are: • accident avoiding effectiveness • injury avoiding effectiveness • injury mitigating effectiveness • effects of tertiary safety functions Some safety functions aim at avoiding the accident altogether. If this is not possible, measures to prevent the involved persons from suffering injuries are taken. If this cannot be achieved either, the injury outcome for the passengers is minimized as far as possible. Afterwards, the aim is to reduce the consequences of already inflicted injuries to the largest extend possible (e.g. by automatically placing an emergency call). A typical primary safety function aims at all of the first three types of effectiveness, whereas the effectiveness of a typical secondary safety function only consists of the injury avoiding and injury mitigating effectiveness. Tertiary safety functions aim at reducing the consequences of injuries. This paper focuses on primary and secondary safety functions and does not deal with tertiary safety functions at all. In some sense the first three mentioned types of safety function effects are ordered hierarchically. A safety function which aims at accident avoiding typically has some measurable effect on injury avoiding and injury mitigating in cases in which the accident can not be avoided but the crash’s severity can be reduced. A secondary safety function aiming at injury avoiding typically also has some effectiveness towards injury mitigating but not towards accident avoiding. Thus, a combined evaluation of different safety functions must include injury avoiding and mitigating effectiveness as well as the accident avoiding effectiveness.