The effects of motor vehicle fleet Daytime Running Lights (DRL) on motorcycle conspicuity

  • Published: U.S. Department of Transportation, National Highway Traffic Safety Administration (NHTSA); Report number DOT HS 811 504, 2011
  • Authors: Pierowicz J, Gawron V, Wilson G and Bisantz A
  • Date Added: 25 Jan 2014
  • Last Update: 25 Jan 2014
  • Format: html


To evaluate the effects of motorcycle conspicuity treatments on other drivers’ left turn gap acceptance. For the U.S. situation, a left-turn means to the offside, crossing the oncoming flow of traffic


In Phase 1, a test track study measured participants’ left turn gap judgment as a function of motorcycle DRL treatments. This study was designed to determine which treatments yielded the largest gaps, thereby making that treatment a good candidate for the on-road portion. No treatment was clearly better, so lighting systems currently in use on motorcycles were selected for the on-road study.

In Phase 2, an on-road study measured gap acceptance, then followed up with intercept surveys of observed drivers. This phase included data collection in the United States (low fleet DRL use) and Canada (high fleet DRL use) in order to evaluate the effect of DRL use in the vehicle fleet.

Key Findings:

  • The treatments: Reduced Intensity Upper Beam, Driving Lights with Lower Beam, and Modulating Lower Beam showed no benefit in gap acceptance during the track trials.

  • Canadian drivers provided longer gaps than American drivers in the baseline conditions. Although, among Canadian drivers, there were no differences between gaps provided to motorcycles and those provided to other traffic.

  • The current data did not allow the authors to determine whether gaps afforded to passenger vehicles with and without DRL were different or not.


Motorcycle conspicuity, Daytime Running Lights, DRL


Unfortunately, several null results.