A possible disadvantage of the use of daytime running lights (DRLs) is an increase in fuel consumption. After all, switching on the lights results in a bigger load on the dynamo. Using conventional dipped headlights for DRL increases fuel consumption by 1-3%, dependent on the fuel consumption of the car. Using dedicated daytime running lights leads to a 50% reduction in fuel consumption by lighting; using LED lights results in a maximum reduction of 90% (see the archived SWOV factsheet Daytime Running Lights (DRL).
Moreover, a recurring supposition is that DRLs for cars reduce the visibility of other road users who do not make use of lights in the daytime, such as pedestrians and cyclists (masking effect). Research has shown, however, that this effect does not occur [37]. Pedestrians and cyclists even seem to benefit from the DRLs used by the cars around them, since they are illuminated by the car lights.
For motor cyclists, vehicle lighting in the daytime has been customary longer than for car drivers. Previously, the use of DRLs was unique to motor cyclists, which made them more conspicuous than other road users. Research has shown that particularly for great distances and on rural roads DRLs of motor cyclists have a positive effect on the visibility of motor cyclists to other road users [38]. The effect of DRLs used by car drivers on the visibility of motor cyclists is not absolutely clear [37] [38].
