Identification and ranking of Black spots: Sensitivity Analysis

Abstract

In Flanders, approximately 1014 accident locations are currently considered as ‘dangerous’. These ‘dangerous’ accident sites or so-called ‘black spots’ are selected by means of their historic accident data for the period 1997-1999. More specifically, a combination of weighting values, respectively 1 for each light injury, 3 for each serious injury and 5 for each deadly injury (combination 1_3_5), is used to rank and select the most dangerous accident locations. In this paper a sensitivity analysis is performed to investigate the impact on the identification and ranking of black spots of 3 different weighting value combinations each representing a different attitude towards the traffic safety problem: avoiding all accidents (1_1_1), avoiding all deadly accidents (1_1_10) and avoiding all accidents with serious or deadly injuries (1_10_10). Results show that a different attitude towards the traffic safety problem and the choice of the corresponding injury weighting values does have important consequences for the selection and ranking of black spots and for traffic safety actions in general. Furthermore, a change in the traffic safety policy and the reflection of this choice in the injury weighting values will not only have an important impact on the number of accident locations that will change when selecting and ranking black spots, it will also have an important effect on the type of accident locations that are selected and accordingly on the resulting future traffic safety decisions.