Performance Implications of Bicycle Specific Treatments at Signalized Intersections

A rise in cycling nationwide has brought an increased awareness of bicycle specific safety concerns, particularly right-hook crashes at signalized intersections. There are several common and emerging signal timing strategies that are can be used to improve the safety and efficiency of traffic signals for people on bicycles, including the Leading Bicycle Intervals (LBI), Split LBI, and Exclusive Bicycle Phasing (EBP). The leading and split bicycle intervals provide a head start for bicycles in advance of concurrent and conflicting motor vehicle movements, typically about 3-5 seconds. The EBP provides an interval only when bicycles are moving. To examine the performance and efficiency metrics under a range of bicycle and motor vehicle volumes, a Vissim microsimulation model was developed. Passenger cars, large trucks, bicycles, and pedestrians were modeled to understand the performance across and between the modes. User delay values were extracted from the model and compared to the base case. A total of 210 simulation runs were conducted, accounting for approximately 262.5 hours of simulation. Results indicate a small vehicle delay increase of between 4% - 11% [as delay in seconds per user] for the Split LBI, with thru traffic (which is unaffected by the Split LBI treatment) virtually unaffected at 1% - 2% delay increases; the LBI saw larger increases in vehicle delay from 11% - 19%; and large vehicle delay increases for the EBP (up to 26% for the eastbound approach), but also found an apparent bias in the coordination scheme that led to decreases for the westbound approach. Bicycle delay results showed more variation with the LBI treatment showing little impact, with results ranging from -5% - 5% changes in bicycle delay. Split LBI showed delay increases of 3% - 11% for the thru cyclists, but mixed results for the right turning cyclists, which showed delay results increasing as a function of bicycle traffic. Bicycle delay results for the EBP showed large increases from 100% - 565%. Pedestrians and left turning vehicles were all but unaffected by either the LBI or Split LBI. While the EBP did show changes in delay as high as 22% for pedestrians. This research demonstrates that bicycle specific treatments do impact user delay at busy arterial intersections, although the magnitude of impact differs depending on the treatment used. The use of the Split LBI had little overall impact, suggesting it is an effective treatment if the intersection configuration is correct. The LBI had greater impact, and should be considered for intersections with the correct configuration. The EBP had large delay increases suggesting limited use, only when bicycle volumes are high enough to justify the delay