Although a relatively minor share of overall travel in the United States, in many regions bicycling is on the rise. At the same time, operating in mixed traffic can increase the likelihood of a bicyclist injury or death in the event of a crash with a motor vehicle. In keeping with Vision Zero and Towards Vision Zero goals, many agencies are seeking ways to provide safety improvements for these vulnerable road users, including the installation of traffic signals with bicycle symbols on the signal faces.
In 2013, the FHWA issued interim approval for the use of bicycle signal faces for particular situations, including providing a lagging or leading bicycle interval; addressing unexpected or unusual arrangements in complex intersections or conflict areas; and in conjunction with a segregated, counter-flow bicycle facility. To date, over 40 state and local highway agencies’ requests for approval to install bicycle signal faces have been approved.
Because general traffic signals and bicycle traffic signals both utilize green, yellow, and red indications, there is concern that road users may confuse the two types of signals. This concern makes some agencies reluctant to implement bicycle signal faces. Although the bicycle signal indication is in the shape of the bicycle, at certain distances or in certain configurations users may confuse the indications intended for the users of the bicycle lane for the general lane, or vice versa. This may be a particular issue where the general travel lanes will be displaying one color (e.g., red), while the bicycle signal will be displaying another color (e.g., green).
Anecdotal evidence from agencies that have installed bicycle signal faces does not suggest road user confusion is an issue, but research on this issue is sparse. Fournier, Christofa, and Knodler used a driving simulator to test driver behavior at intersections with sharrows, bike lanes, bike merge-lanes, and bike boxes and found driver compliance was largely associated with the level of familiarity with a particular treatment and test subjects’ bicycling experience (see Bicycle Infrastructure from the Driver’s Seat: Evaluating Bicycle Infrastructure Using a Driving Simulator, published in the Proceedings of the 96th Annual Meeting of the Transportation Research Board, 2017). As bicycle signal faces are used only infrequently in the United States, a lack of familiarity with these signals may reduce their effectiveness in maintaining traffic flows, reducing conflicts, and improving safety. A focused study is needed to provide information for agencies considering the use of bicycle signal faces and for those entities responsible for developing guidelines and standards for traffic control devices.
The objective of this research is to summarize and synthesize the U.S. experience with bicycle signal face installations, with particular focus on how drivers of motor vehicles comprehend and comply with traffic signal installations where bicycle signal faces and circular signals are located at the same intersection approach. The research will also identify how any remaining gaps in understanding driver comprehension and compliance can be effectively addressed through further research.