Feasibility and acute alerting effects of a daylight-supplementing in-vehicle lighting system – Results from two randomised controlled field studies during dawn and dusk

Abstract

The present studies examined the feasibility and acute alerting effects of additional in-vehicle lighting within a passenger car. These factors were examined during morning driving (Study 1) and evening driving (Study 2). In a balanced within-subjects design, 37 participants drove a test car two times in the morning or in the evening. The test vehicle was equipped with either a daylight-supplementing interior lighting system or a placebo system, which participants were told would refresh the air. Both studies used identical protocols, and participants participated either in Study 1 ( n = 18) or Study 2 ( n = 19). In both studies, corneal illuminance levels were recorded while driving. Feasibility of the systems was assessed using subjective ratings. Efficacy outcomes were spindle rates in the alpha bandwidth of electroencephalogram recordings, performance on a psychomotor vigilance task and subjective sleepiness ratings. In both studies, daylight-supplementing significantly increased corneal illuminances while driving and did not cause any negative visual side-effects. Study 1 revealed lower spindle rates while driving under daylight-supplementing lighting, indicating that drivers had higher physiological alertness when exposed to additional light in the morning. This alerting effect of daylight-supplementing lighting, however, was not observed in Study 2. In both studies, performance on the psychomotor vigilance task as well as subjective sleepiness ratings did not significantly differ between the experimental conditions. The present studies provide novel evidence for the feasibility and positive impact of daylight-supplementing in-vehicle lighting systems on the physiological alertness of drivers under naturalistic driving conditions. Further studies are warranted to evaluate carry-over effects of increased alertness on road safety measures.