Evaluation of Bike Boxes at Signalized Intersections

Jennifer Dill, Portland State University



The American Community Survey, an annual survey conducted by the US Census Bureau, has recorded a 145% increase over ten years (from 1.8% in 1996 to 4.4% in 2006) in Portland, Oregon residents choosing the bicycle as their primary means of transportation for commuting to work. Despite this increase in bicycling activity, recent surveys have found that more than half of Portland residents limit their bicycling due to traffic safety concerns. Analyses of motor vehicle and police reported crash data reveal that nearly 68 percent of bicycle crashes in Portland occur at intersections (PDOT, 2004) which are consistent with national trends (Hunter et al., 1996). Of these intersection crash types, a common crash pattern is the “right-hook” where right-turning motorists collide with through or stopped bicycles. This conflict occurs whether or not a bicycle-lane is present; however, the presence of a bicycle lane adds additional complexity to safe design and operation of the intersection. To partially address these conflicts between bicycles and right-turning motor vehicles, the City of Portland will be installing up to 12 “bike boxes” (also known as advanced stop line or bar) at signalized urban intersections. As proposed, the typical installation consists of an advanced stop line, green textured thermoplastic marking with bicycle stencil, intersection striping, and regulatory signage (including no-turn-on-red). The box is located in front of the stop line for motor vehicles and behind the pedestrian crosswalk. These installations also include colored bicycle lane markings in the intersection which is unique. This combination of traffic control is hypothesized to reduce conflicts between motor vehicles and bicyclists and make motorists aware of a potential conflict. An additional desired secondary outcome would be to encourage more bicycling by enhancing safety and priority at an intersection. This installation provides a tremendous research opportunity for several reasons. First, while it appears that the application of these traffic control devices will improve safety, it is not clear how they will perform under actual conditions. Second, such an application of bike boxes in the U.S. is unprecedented. Bike boxes and similar advanced stop lines are used extensively in the United Kingdom, the Netherlands, Denmark, and other European countries. Thirdly, comprehensive evaluations of bike boxes are rare. We propose conduct a comprehensive, classical, observational before-after study of the effectiveness of the installed experimental traffic control devices and responses of all system users impacted by the installation of the bicycle boxes. Our approach will answer such research questions as: 1. Do the bike boxes reduce conflicts or the potential for conflict between motorized vehicles and bicycles? 2. Do the bike boxes create any new or potential conflicts between motorized vehicles and bicycles? 3. How does motor vehicle driver and bicyclist behavior differ with and without the bike boxes? 4. What design features affect behavior and conflicts? 5. Do the bike boxes affect pedestrian safety, behavior, or conflicts with motor vehicles or bicyclists? 6. What are the impressions of the drivers and bicyclists using the intersections about how the bike boxes affect safety and operations? Two primary research methods will be employed: (1) before and after video surveillance of the intersections where bike boxes will be installed and appropriate control intersections; and (2) surveys of cyclists and drivers. The video surveillance will address most of the research questions in an objective manner.

Project Details

Project Type:
Project Status:
End Date:
January 31,2010
UTC Grant Cycle:
OTREC 2009
UTC Funding: