Monday, March 4, 2013

Bike Signals State of the Practice

North American cities have been making huge leaps in creating safe places to bike in recent years. The National Association of City Transportation Officials (NACTO) recently published the Urban Bikeway Design Guide to describe the best practices that can be used to improve conditions for cycling and includes a section on bicycle-specific signals. Bicycle-specific traffic signals are used at intersections with conventional signals to specifically control cyclists’ movement and were recently reported on by USA Today. Though use of bicycle-specific signals are limited by the US Manual on Uniform Traffic Control Devices (MUTCD) there is still considerable experience with bicycle-specific signals in North America.
The morning rush on the Broadway Bridge in Portland, OR. Signals controlling motor vehicles, bicycles and streetcar keep orderly flow. The photo inset shows the detail of the bicycle signal head. Photo P. Koonce

In a soon to be published paper in the TRB’s Transportation Research Record, researchers at Portland State University—in collaboration with engineers from the Portland Bureau of Transportation and the Oregon Department of Transportation—summarize the results of a recent state-of-the-practice review related to bicycle-specific signals. The review included two components: 1) a review of related engineering guidance documents:

·         Manual on Uniform Traffic Control Devices (MUTCD) (FHWA, 2009)
·         Traffic Signal Guidelines for Bicycles (Transportation Association of Canada (TAC), 2004)
·         Manual of Uniform Traffic Control Devices for Canada, 2008 update (TAC, 2008)
·         Design Manual for Bicycle Traffic (CROW, 2007)

and 2) a survey sent to jurisdictions with known bicycle-specific signals.  Survey responses were received from 15 of the 21 jurisdictions, representing 63 intersections which contained a total of 149 separate bicycle-specific signal heads. Jurisdictions included in the survey are shown as black boxes within the figure:

Jurisdictions identified with bicycle-specific signals and survey respondents. Note numbers following the “:” denote the number of reported signal heads at that location, jurisdictions with a ‘U’ value did not respond to the survey.

The paper summarizes both physical and operational design guidance. Physical elements reviewed include details about the suggested size of lens, the use of bicycle insignia within the lens, color and presence of backplates, and placement of the signal head. The review of the operational elements include details about the bicycle-specific signal’s detection, phasing, restricted movements for other modes, accompanying signage, and intervals for cyclists to safely cross the intersection. Overall, while there were minor differences between the guidance documents, the guidance was generally consistent.

This survey requested detailed engineering aspects about each jurisdiction’s bicycle-specific signal that they were operating, the topics of which were previously mentioned (placement, mounting height, lens diameter, backplate and housing color, type of actuation, interval times, use of louvers, and performance). The survey of practice found a variety of design elements: lens size, use of insignia, utilization of louvers, mounting location, and the means to designate that the signal head is for bicyclists. These elements could have significant impact on bicyclist and motorist comprehension, as well as the ability to utilize the bicycle signal head in a variety of intersection configurations. Some consensus appears on the use of the lens insignia and accompanying signage. Another part of the survey asked for motivating reasons as to why the jurisdiction had decided to install a bicycle-specific signal at each respective intersection, allowing multiple reasons to be cited. Responses were grouped into five categories: ‘cyclist non-compliance with previous traffic control’, ‘presence of a contra-flow bicycle movement’, ‘a diagonal (or otherwise unique) cyclist path through the intersection’, ‘safety concerns for cyclists’, and ‘other’. The survey responses indicated that bicycle signals are most commonly installed when cyclists are moving against motor vehicle movements, taking a non-standard path through an intersection, or when there are safety concerns for cyclists at that intersection. Many signals in Vancouver, BC and Montreal, QC are used to control contra-flow movements on two-way cycle tracks.

Bicycle-specific traffic signals are common in many places throughout Europe, however, they are a new tool for transportation engineers in North America. The availability of engineering guidance has improved substantially over the past few years with the release of the California MUTCD, NACTO’s Urban Bikeway Design Guide, and AASHTO’s guidance. While there are minor differences, there is generally consistent guidance. To some extent, the guidance documents reflect the lessons learned by the surveyed jurisdictions since installation of the bicycle-specific signals is limited to those places willing to experiment. The survey of practice found a variety in some design elements: lens size, use of insignia, utilization of louvers, mounting location, and the means to designate that the signal head is for bicyclists. Some consensus appears on the use of the lens insignia and accompanying signage. Given the accelerated deployments of bicycle-specific signals and the new guidance documents, it is likely that there will be less variety in future designs. Adoption of minimum guidance in the U.S. MUTCD would also likely improve consistency and practice. The National Committee on Uniform Traffic Control Devices is presently considering language addressing bicycle-specific signals.

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