SWOV Catalogus


Daytime Running Lights for cars : analysis of the effect on traffic safety.
20170490 ST [electronic version only]
Kühn, M. (Ed.)
Berlin, German Insurance Association (Gesamtverband der Deutschen Versicherungswirtschaft GDV), 2011, 9 p., 4 ref.; Compact accident research ; No. 24

Samenvatting The European Commission has decided that new types of passenger cars have to be equipped with dedicated Daytime Running Lights (DRL) from 07.02.2011 on. DRL are considered as a long-lasting and energy-saving alternative to low beam headlights and are supposed to increase traffic safety. Studies indicate a considerable decrease in accident numbers. Estimations on a conservative basis average out at 3 to 4 %. Its opponents however fear for the safety of vulnerable road users. On behalf of German Insurers Accident Research (UDV) Human-Factors-Consult GmbH examined safety effects and risks of DRL in cooperation with the department of Lighting Technology of the Technical University of Berlin. The following research questions were addressed: * Evidence of safety effects and risks: Which effects do DRL have for car drivers and vulnerable road users? * Comparison of selected accident types: Do they show different DRL-related effects? * Assessment of the sustainability of effects: Do they even out over time due to habituation? * Control of demographic and situational characteristics: Do they moderate the effects of DRL? * Comparison of low beam headlights as DRL and dedicated DRL: What difference does it make? Within the 2.5-year project period three empirical studies were carried out: (1) Driving study including gaze measurement in Germany and Denmark (2) Laboratory study in the light tunnel of the Technical University of Berlin (3) Driving Simulator study assessing gaze and driving behaviour. By choosing different methodical approaches it was possible to analyse various aspects in detail, and to mutually validate the results. It also combined experimental control with evidence of the transferability of results in real traffic. At the beginning of the project reviewed literature was classified by selected criteria and assessed regarding methodical quality and explanatory value. It was thereby possible to identify credibly substantiated effects from statements that lack significance. Most of the studies are based on accident statistics for car models equipped with or without DRL (low beam) or on national accident statistics. They compare accident numbers before and after the use of running lights at daytime has become mandatory. Their reported decreases in accident numbers often reach double digits and are mostly not statistically significant, i.e. they are due to random deviations. These are often misinterpreted as safety effects, which eventually leads to predictions of accident decreases up to 25%, even though neither safety effects nor risks are sufficiently substantiated. Accident studies fail to separate the effect of DRL from confounding factors (e. g. fleet studies and national studies) or lack sufficient number of cases (experimental design) to conduct a well-founded statistical analysis. Studies conducted in the laboratory prove a significantly improved perceptibility for cars with running lights at daytime, while a disadvantage for vulnerable road users has not been verified so far. For methodical reasons the transferability of these results in real traffic cannot be assumed. A driving study interprets slightly longer gaze durations for cars with lights switched on as a DRL-induced gaze capture and hence assumes negative effects for vulnerable road users. The sometimes pronounced position pro vs. contra DRL is surprising, the more so as neither advantages and risks of DRL nor their mode of action (attention allocation, gaze capture) have been convincingly supported. (Author/publisher)
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