Effectiveness of light-reflecting devices: A systematic reanalysis of animal-vehicle collision data

Abstract Every year, approximately 500 human fatalities occur due to animal-vehicle collisionsin the United Statesand Europe. Especially heavy-bodied animals affect road safety. For more than 50 years, light-reflecting devices such as wildlife warning reflectors have been employed to alert animals to traffic when crossing roads during twilightand night. Numerous studies addressed the effectiveness of light-reflecting devices in reducing collisionswith animals in past decades, but yielded contradictory results. In this study, we conducted a systematic literature review to investigate whether light-reflecting devices contribute to an effective prevention of animal-vehicle collisions. We reviewed 53 references and reanalyzed original data of animal-vehicle collisionswith meta-analytical methods. We calculated an effect sizebased on the annual number of animal-vehicle collisionsper kilometer of road to compare segments with and without the installation of light-reflecting devices for 185 roads in Europe and North America. Our results indicate that light-reflecting devices did not significantly reduce the number of animal-vehicle collisions. However, we observed considerable differences of effect sizeswith respect to study duration, study design, and country. Our results suggest that length of the road segment studied, study duration, study design and public attitude (preconception) to the functioning of devices may affect whether the documented number of animal-vehicle collisionsin- or decrease and might in turn influence whether results obtained were published.