This project was funded by the National Institute for Transportation. This project was also funded by the New York City Department of Transportation and City of Phoenix Street Transportation Department. The authors are thankful to Nolan Levenson, Carl Sundstrom, Peter Koonce and Oliver Smith for their assistance with field deployment and data procurement. The authors would also like to thank Dan Brandesky from Econolite Corporation for his assistance with the simulation.
Traffic safety -- Oregon -- Portland, Cycling accidents -- United States -- Prevention
Over the last decade there has been increased interest in promoting active and sustainable transportation modes such as bicycling and walking especially in urban areas, as a means to alleviate congestion, lower emission levels and improve personal health. In urban areas, intersections are locations where a variety of modes converge, thus increasing the propensity for conflicts. Many bicycle-vehicle crashes occur at intersections. A common crash type involving bicycles at intersections is the “right-hook” where a right-turning vehicle collides with a through bicyclist. Intersections are also the source of increased stress for many bicyclists where the interactions with cars are more pronounced. Geometric treatments such as pavement markings, bike boxes, colored lanes, and shared right-turn lane designs have been implemented in an attempt to alleviate the problem. While the use of signal timing treatments has been limited until now, cities are beginning to explore treatments such as leading bicycle intervals, split leading bicycle intervals and exclusive phasing using bicycle specific signals. While exclusive phasing eliminates the bicycle-vehicle conflict by separating the phases and restricting turns, the trade-off is a decrease in efficiency at the intersection with increased delays for all users. An emerging operational treatment at intersections is to provide a split leading bicycle interval (split LBI), with concurrent green for bicycles, pedestrian walk and green for the through vehicles while restricting or essentially delaying the right turn for vehicles. After a certain time, the restriction on turns is lifted. The same treatment could also be used for pedestrians and offers advantages over the traditional leading bike and pedestrian intervals (LBI, LPI) in that there is no lost time for through vehicles. This study will evaluate various signal timing control strategies that are designed to minimize conflicts between bicycles, pedestrians and turning vehicles using micro simulation, deployment and video based conflict analysis to study efficiency and safety impacts.