Bicycling is increasing in the United States – the number of trips made by bicycle more than doubled from 1.7 billion trips in 2001 to 4 billion in 2009 (NHTS, 2009). With the increase in bicycling rates, there is a critical need for cycling infrastructure, which includes on and off road bicycle lanes and paths, separated lanes, improved intersection designs, pavement markings, bike boxes, two-stage turn boxes, and bicycle-specific traffic signals. These traffic signals, which have a red-yellow-green bicycle stencil display in the signal face, are used to implement leading intervals, to signalize bicycle-only approaches, and to separate conflicts between turning motorists and through cyclists (especially on two-way bicycling facilities). They are common tools in the European low-stress bicycling network, where cycling is popular.
Prior to December 2013 when FHWA issued Interim Approval 16 “Interim Approval for Optional Use of a Bicycle Signal Face” (IA-16), the use of bicycle-specific signals in the U.S. was limited. A research team led by this proposal’s PI, Monsere, published “Operational Guidance for BicycleSpecific Traffic Signals in the United States” for the Oregon DOT that included a review of the state of the practice for North American use of bicycle-specific traffic signals(Monsere et al, 2013). The review identified 86 intersections using 149 bicycle signal faces in the U.S. and Canada (34 intersections were in the U.S.). The research collected detailed information such as the presence and color of backplates, signal housing color, lens size, presence of visibility limiting lens or louvers, near-side or far-side placement, mounting height, phasing, restriction on vehicle movements, and supplemental signage. At the time of the review, only California allowed the use of a bicycle signal face in traffic signal displays. A few jurisdictions outside California had been using the Manual on Uniform Traffic Control Devices (MUTCD) experimental process to test bicycle signals such as Arlington, VA, Boulder, CO, and Chicago, IL. Following the approval of IA-16 (which cited the Oregon DOT research in its summary statement), the number of U.S. installations of bicycle-specific traffic signals has steadily increased. As stated in the RFP, over 40 state and local highway agencies have requested approval to install bicycle signal faces under IA-16. The Bicycle Technical Committee of the National Committee on Uniform Traffic Control Devices (NCUTCD) has been compiling a list of installations. The list has currently identified over 490 intersections in the U.S. (193 of them in New York City, NY) with bicycle signals.
The motivation for this research – to develop a better understanding of how and when drivers of motor vehicles confuse bicycle signal faces with circular signal faces – has been a consideration for designers for some time. The guidance in the MUTCD (2009), IA-16, and NACTO’S Urban Bikeway Design Guide (2011) note that the placement of bicycle signal faces should maximize visibility for bicyclists and minimize visibility for drivers. The guidance suggests the use of visibility-limited bicycle signal faces when necessary and requires the use of the R10- 10b “Bike Signal” sign to enforce the signal face as bicycle-specific. Further, IA-16 requires that the bicycle signal face be “separated vertically or horizontally from the nearest motor vehicle traffic signal face for the same approach by at least 3 feet”.