Risk compensation--the case of road lighting.

The hypothesis of this article is that drivers will not adjust their behavior, i.e. drivers are not expected to increase their speed, reduce their concentration or travel more when road lighting is installed. The hypothesis was based on previous research showing that road lighting reduces road accidents and that average driving speeds do not increase when road lighting is installed. Our results show that drivers do compensate for road lighting in terms of increased speed and reduced concentration. Consequently, the hypothesis is rejected. This means that road lighting could have a somewhat larger accident-reducing effect, if compensation could be avoided. The fact that previous research has found no change in average speed when road lighting is introduced, seems to be explained by increased driving speeds by some drivers being counterbalanced by a larger proportion of more slowly driving groups of drivers (elderly people and women), i.e. different subgroups of road users compensate in different ways.