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The Effects of Motor Vehicle Fleet Daytime Running Lights (DRL) on Motorcycle Conspicuity

As a group, motorcyclists experience a high fatality rate, a significant number of which are attributable to right-of-way violations by other drivers. One factor behind the high crash rate is insufficient conspicuity of motorcycles, which is now of greater concern because of the increasing use of Daytime Running Lights (DRL) in the vehicle fleet. The hypothesis is that the additional lights on all vehicles will degrade the conspicuity of the previously unique DRL signal used by motorcycles. The main goal of the current study was to evaluate the effects of motorcycle conspicuity treatments on other drivers’ left turn gap acceptance. This study was comprised of three phases. 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. However, due to concerns about the comparability of the U.S. and Canadian data, the results are inconclusive, and additional research is suggested. In Phase 3, motorcycle side conspicuity treatments (retro-reflectors and marker lamp) were compared. Results indicated that there were no differences in detection distance between the treatments.