The importance of road environment factors for road safety research at the example of black spot treatment

Within the scope of this study a standardized assessment of safety and economic efficiency was conducted concerning countermeasures at black spots on country roads. Thereby one was able to benefit from comprehensive detailed Bavarian data material of high quality. The evaluation of effectiveness was based on "before-after" comparisons concerning accident occurrence, whereby adequate random tests have been performed in order to obtain sound conclusions - taken into account "bias by selection". A total of 2,419 accident striking road sites or sections have been investigated and evaluated. Regarding all investigated measurements for improving traffic safety together, a significant increase in safety could be recorded. The derived economic benefit of these measurements exceeded the financial expenses by a factor of over 12. The large reduction of black spots was also resulting in a positive accident record relating to the total net. For example, as a consequence of the countermeasures applied at black spots the netwide accident cost rate is decreasing by approximately 50 %. (A)