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Abstract
The number of fatal crashes on United States roadways has declined substantially since 2002, yet the number of fatalities involving two-wheeled motorists has consistently increased over the same period. Examining incidents involving a two-wheel motor vehicle and a passenger vehicle indicates passenger car drivers often fail to recognize an oncoming two-wheeler and unintentionally violate their right of way. This reoccurring scenario has raised questions surrounding the visual performance capabilities of drivers. Numerous studies have investigated ways to increase the conspicuity of two-wheelers under daytime conditions, such as adding daytime running lights, but only a few have analyzed their conspicuity under nighttime conditions. The aim of this study was to evaluate the visibility of several hazards that drivers encounter at urban intersections under nighttime conditions, including passenger vehicles and two-wheeled motorists. The 30 participants who took part in this study interacted with a low fidelity simulator which presented a series of videos from a driver's perspective while the vehicle was positioned in the permitted left turn lane at a signalized intersection. During each video the participant was instructed to determine whether a left turn maneuver was safe to make given the current traffic conditions. If a hazard was present, such as an oncoming vehicle or a pedestrian, participants were asked to identify the hazard. The response times for each participant were recorded, for a total of 627 responses. The results indicate there is no significant difference in a driver's ability to recognize a two-wheeled motorist compared to a passenger vehicle at urban intersections where street lighting is installed. Therefore, the conspicuity issues for two-wheelers in daytime and nighttime conditions are not the same. Furthermore, the same treatments proposed for two-wheelers in daytime conditions may not be as beneficial or even needed during nighttime driving. However, analysis of other hazards revealed that as a hazard becomes more complex and is no longer emitting light, recognition time is extended. Future studies are proposed to determine if the same results hold true at rural intersections where artificial lighting is not provided.