RWS-Fileproof wanted to know if and how safety and traffic flow at the location of an incident are affected when police and rescue vehicles carry one or more flashing lights. In a simulator experiment 64 subjects were exposed to different configurations of flashing lights while the authors measured their driving behavior. The incident was always preceded by a vehicle carrying either a blue or amber (orange) flashing light and two rescue vehicles behind the incident carried either blue lights or none at all (as suggested by the guideline 'flashing lights off at location'). Looking at average speed and its standard deviaton the authors saw clear effects of the flashing lights. Moreover, there was an 'authority effect' of the color: the more flashing lights were visible, the earlier a reduction in driver speed could be observed. At day time this effect was even larger than in the evening. The observed changes in lateral position throughout the experiment cannot be distinguished statistically between the conditions. Based on the results of this study the authors conclude that displaying multiple flashing lights affects driver speed more than a single light does. This has however, no consequences for safety as they did not find differences in lateral position between the conditions. As the authors know that irregularities in the traffic flow increase the risk on accidents it seems to be justifiable to state that the guideline 'flashing lights off at location' can contribute to reduction of traffic-jams at an accident location without decreasing the traffic safety and safety of police and rescue officers. (Author/publisher)
Samenvatting