In-car nocturnal blue light exposure improves motorway driving: a randomized controlled trial

PLoS One. 2012;7(10):e46750. doi: 10.1371/journal.pone.0046750. Epub 2012 Oct 19.


Prolonged wakefulness greatly decreases nocturnal driving performance. The development of in-car countermeasures is a future challenge to prevent sleep-related accidents. The aim of this study is to determine whether continuous exposure to monochromatic light in the short wavelengths (blue light), placed on the dashboard, improves night-time driving performance. In this randomized, double-blind, placebo-controlled, cross-over study, 48 healthy male participants (aged 20-50 years) drove 400 km (250 miles) on motorway during night-time. They randomly and consecutively received either continuous blue light exposure (GOLite, Philips, 468 nm) during driving or 2*200 mg of caffeine or placebo of caffeine before and during the break. Treatments were separated by at least 1 week. The outcomes were number of inappropriate line crossings (ILC) and mean standard deviation of the lateral position (SDLP). Eight participants (17%) complained about dazzle during blue light exposure and were removed from the analysis. Results from the 40 remaining participants (mean age ± SD: 32.9±11.1) showed that countermeasures reduced the number of inappropriate line crossings (ILC) (F(2,91.11) = 6.64; p<0.05). Indeed, ILC were lower with coffee (12.51 [95% CI, 5.86 to 19.66], p = 0.001) and blue light (14.58 [CI, 8.75 to 22.58], p = 0.003) than with placebo (26.42 [CI, 19.90 to 33.71]). Similar results were found for SDLP. Treatments did not modify the quality, quantity and timing of 3 subsequent nocturnal sleep episodes. Despite a lesser tolerance, a non-inferior efficacy of continuous nocturnal blue light exposure compared with caffeine suggests that this in-car countermeasure, used occasionally, could be used to fight nocturnal sleepiness at the wheel in blue light-tolerant drivers, whatever their age. More studies are needed to determine the reproducibility of data and to verify if it can be generalized to women.

Trial registration: NCT01070004.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Automobile Driving*
  • Caffeine / pharmacology
  • Coffee / chemistry
  • Cross-Over Studies
  • Double-Blind Method
  • Fatigue / prevention & control*
  • Humans
  • Light
  • Male
  • Middle Aged
  • Photic Stimulation*
  • Placebos
  • Psychomotor Performance / drug effects
  • Psychomotor Performance / radiation effects
  • Reproducibility of Results
  • Sleep Deprivation
  • Sleep Stages / radiation effects
  • Wakefulness / drug effects
  • Wakefulness / physiology
  • Wakefulness / radiation effects*


  • Coffee
  • Placebos
  • Caffeine

Associated data


Grants and funding

This research was supported by an ERANET transport ENT 15 grant (Sleepiness at the wheel) from the French Ministry “Ministère de l'Ecologie, du Développement Durable, des Transports et du Logement (MEDDTL)”. PHILIPS provided 2 portable blue lights (goLITE BLU®) and VINCI autoroute/ASF allowed us to use their highways for our research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.