The role of protected intersections in improving bicycle safety and driver right-turning behavior.

Protected or separated bike lanes or cycle tracks, are increasing in popularity in North America and Europe. However, despite their documented benefits, there are concerns about potential conflicts between bicycles and vehicles when they merge back together at an intersection. The concern is that following a period of separation, drivers are less likely to anticipate and scan for the presence of bicyclists. This research examines how transitions from fully separated to mixed-traffic environments and vice versa affect driver behavior. The goal is to assess whether certain segment-intersection treatment combinations can alert drivers of the presence of bicyclists and thus, encourage them to scan for bicyclists prior to a right turn, reducing potential right-hook conflicts. Driving simulation is utilized and driver performance for right-turning vehicles is recorded under the presence of various bicycle infrastructure treatments along segments and at intersections. The experimental design includes conventional and protected bike lanes and intersections with either intersection crossing markings or protected intersections. The results show that the presence of protected bike lanes motivates fewer glances towards bicyclists traveling on those bike lanes, therefore, reducing drivers' ability to detect and in turn, perceive bicyclists. Drivers developed slightly lower speeds while driving next to protected versus conventional bike lanes. It was also found that protected intersections result in a higher rate of right glances at the intersection prior to a right turn. Drivers glancing at the intersection were also found to have lower speeds, indicating a correlation between the presence of protected intersection elements and speed selection. This research can be used to guide decisions on bicycle infrastructure implementation for safer multimodal operations.