Bicycle Safety Guide and Countermeasure Selection System
Sign explaining the green wave on Valencia Street in San Francisco. Photo by Bryan Goebel
Traffic signals are installed at intersections to improve operations and efficiency and should be designed to accommodate all users. An engineering study should be conducted to determine if a signal is the most appropriate traffic control device, in accordance with Part 4 of the Manual on Uniform Traffic Control Devices (MUTCD). The overall goals of signal timings are to provide safe crossings and reduce delay for all users. Two primary means to accomplish this are by: 1) adjusting timings at individual intersections, and 2) adjusting coordination settings at a series of intersections.
Signal timing is a key strategy to reduce delay and to encourage compliance at signalized intersections. Traditionally, signal timing has focused on the efficient movement of motor vehiclesmaximizing motor vehicle throughput and minimizing motor vehicle delay. Signal timing should be analyzed and optimized to accommodate all modes of transportation including bicyclists, pedestrians, motor vehicles, and transit vehicles. Bicycles have different operating characteristics (i.e., speed, acceleration, and deceleration) than motor vehicles. Adjustments to minimum green intervals, red clearance time, and extension time should be considered to ensure that bicyclists can safely cross intersections. Particular consideration should be given to signal timing at locations with high vehicular speeds and long crossing distances. At these locations, bicyclists are more likely to have different signal timing needs than motorists. Additionally, cycle length should be minimized to reduce delay and increase compliance for all users.
Another strategy in signal timing is coordinating signals to provide a "green wave." In a green wave, signals along a corridor are timed such that vehicles will receive a green indication and not be required to stop if vehicles progress at a certain speed. Signal progression speeds should include considerations for bicyclists' operational characteristics. Several cities including Portland, Oregon, and San Francisco, California, have implemented green waves for bicycle speeds. An additional advantage of coordinating signals using a bicyclist's speed is that motorists' speeds are also reduced, creating a more comfortable environment for all users.
Traffic signal timing should be optimized to account for bicycle operating characteristics that include providing minimum green intervals, red clearance time, and extension time to ensure that bicyclists can safely cross intersections.
See countermeasure costs for bike-activated signals.
Authors and Acknowledgements