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Daytime Running Light (DRL)
The effects of daytime running lights on safety continue to be the subject of controversy in discussions between experts. Some of the results from previous studies have indicated clearly positive effects on road safety, while others have indicated there is a danger to unprotected road users – above all, motorcyclists.
Previous studies evaluating the effect of daytime running lights based on numbers of accidents have only rarely been very meaningful. The number of cases in the experimental samples has not been high enough. Field studies carried out up to now with measurements of eye movements have been limited to simple situations and had small samples. Thus studies have not been sufficiently realistic, and the procedure has unfortunately often been unclear, which diminishes the credibility of the conclusions drawn. The field tests in this research project were carried out in Germany and Denmark. The focus was placed on five accident blackspots identified in advance and on positive and negative consequences for both multi-track vehicles and, in particular, more vulnerable road users. The data was collected in the cities of Flensburg and Sonderborg from September 2009 to mid-October 2009.
Light tunnel tests
In the light tunnel of the Lighting Technology department at the Technische Universität Berlin, 20 subjects were shown a road traffic scene involving a car and, in each case, a more vulnerable road user (a pedestrian, a cyclist, a motorcycle in front of a car and a motorcycle next to a car) for a short period (120 ms). The tests were carried out in two different ambient light conditions (broad daylight and twilight). The subjects sat in an illuminated cabin in order to simulate conditions in natural daylight. While doing the object identification exercise, the subjects also had a continuous additional task (tracking) to carry out. This was the equivalent for the subject of a driver’s primary task, which is to actually drive the vehicle.
In the simulator, 20 subjects drove through different intersection situations that represented the accident blackspots. The age range of the subjects was from 19 to 28 years old. A number of parameters were documented, including the eye movements of the subjects. The design of the experiment was based on the gap acceptance paradigm.
One finding of the UDV’s research project is that most previous studies of daytime running lights do not provide reliable data. That applies both to studies finding that daytime running lights have a positive effect on safety and to studies finding that they have a negative effect. This can be attributed, for example, to the complexity of the issue and the associated high costs of such studies if they are to deliver statistically significant results. In particular, in the great majority of cases it is questionable whether the findings of studies carried out in other countries – and the effects on safety that have been deduced – are applicable to Germany.
No appreciable positive effects of daytime running lights on road safety were found in the UDV study. However, after extensive testing in the light tunnel, simulator and real traffic conditions on the road, no negative safety-related effects on more vulnerable road users could be found either. The gaze of drivers is not “locked in” by daytime running lights, nor are more vulnerable road users seen either later or not at all. This also applies to motorcyclists, who have already been using their lights during daylight.