Identification of Safety Critical Events: Development of a new innovative method
When evaluating the safety effects of emerging in-vehicle systems, for natural reasons, crash data cannot be used (they are relatively few and ethically indecent waiting for them to occur). Hence, we need safety indicators occurring more frequently than accidents. It is known that the probability of being involved in safety critical events, including accidents, increases as the as the number of errors in the driving increases, especially tardy decelerations, too short headway to the vehicle in front and poor speed adaption to the traffic situation (Risser 1985). Although these high risk events are more frequent than accidents they are not easy to measure or observe as they occur randomized in place and time, hence there is a need of a new method for identifying safety critical events that can be used in longitudinal studies.
The project aim to assess the relationship between self reported accident involvement and the occurrence of safety critical events in the driving and examine if the method would be able to distinguish safety critical events from non safety critical events. These two different kinds of braking events has shown similar levels of acceleration forces in previous studies (van der Horst, 1990; Várhelyi, 1998; Wahlberg, 2000; Malkhamah et al., 2005; McLaughlin et al., 2008) and it has not been possible to distinguish one event from the other.
Safety critical events are measured in terms of jerks, which is a measure of the abruptness in an evasive manoeuvre, i.e. the rate of change in the acceleration of the vehicle, the second derivate of speed. High risk behaviour decreases the safety margins for road users to compensate for their own or other road user’s errors in traffic (Risser 1985) suggesting that driver’s need to act more sudden and with lesser possibility to plan their actions in these situations. It is thus expected to see an increased amount of jerks amongst driver involved in accidents than drivers that have not been involved in accidents.
Ph D thesis: ”The development of methods for detection and assessment of safety critical events in car driving”, October 2012, Lund University.