Analyses of motor vehicle and police-reported crash data reveal that nearly 68 percent of bicycle crashes in Portland, Oregon occur at intersections (PDOT, 2004) which is consistent with national trends (Hunter et al., 1996). Hunter et al. (1996) also found that 12.2% of crashes involving bicyclists and motor vehicles occurred when a motorist turned or merged into a cyclist's path. Of these intersection crash types, a common crash pattern is the "right hook," where right-turning motorists collide with through or stopped bicycles. One treatment to ameliorate these crashes and conflicts is the installation of the so-called "bike box." Commonly known outside the United States as advanced stop boxes or advanced stop lines, bike boxes are found in the many bicycle-friendly countries. In 2008, the City of Portland completed the first large-scale installation of this treatment in the United States, installing 12 boxes at location in the central core. 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). Collaborating with the City of Portland, OTREC funded an evaluation (which at the time of this proposal is in the final stages of being completed). The research analyzed both before-after video data and comprehension/perception surveys of motorists and bicyclist. Based in part on the results of this first evaluation (Phase 1), the City of Portland is planning to install additional bike boxes. In our first study, we sought to answer questions of compliance and comprehension (e.g. Did the motorist comply with the traffic control and stop prior to the box? Did the cyclist use the box correctly?) as well as safety performance. As such, we focused our video analysis in the peak hours and collected very detailed data about every cyclist and right-turning or stopping motor vehicle. Compliance questions were easily answered from this large sample (3,722 cyclists and 4,163 motor vehicles); comprehension and perceptions were also easily analyzed from the survey results (468 cyclist and 717 motorists). However, only a small number of conflicts were observed (20 before and 14 after). In this extension, we propose to focus primarily on developing a larger sample of conflicts. We will use lessons learned in the first phase to improve our data collection and reduction methodologies. Our proposed approach will increase the sampling period for the before and after periods such that there are more observations of cycle and vehicle interactions. We have a well-designed, documented and repeatable video data reduction method, however, we plan to explore the use of software to automate and screen large quantities of video data for conflicts (e.g. Laureshyn, et al., 2009, Ismail et al. 2009, Sakshaug et al., 2009). In addition to a larger sample, we will collect more robust and detailed video data at the treated locations such that we have complete picture of the operation of the intersection. This will be accomplished using high-quality synchronized digital video (showing views of the box location, the upstream leg, and turning leg) for approximately 12 hours per day (7 am to 7 pm) for 1 week before and after installation. These additional views will allow us to fully evaluate the interactions between all users. We also plan to leverage our new access to the City's central traffic signal system to log signal timing parameters. At certain locations, we have the ability to configure detection loops for counting purposes. This project directly addresses the OTREC's theme of healthy communities and three emphasis areas outlined in this Request for Proposals. Bike boxes are intended to improve the safety of cyclists and, by doing so, increase the amount of cycling. If the evaluation finds that bike boxes meet their safety objectives, installation may become more widespread. This can improve health directly by reducing conflicts between cyclists and motor vehicles and indirectly by increasing the amount of cycling and, therefore, physical activity (Pucher et al., 2009).