Signal Spotlight: Bicyclists at Signalized Intersections

As towns develop multimodal transportation plans, signalized intersections should be considered. According to the 2021 Traffic Safety Facts published annually by the National Highway Traffic Safety Administration (NHTSA), 27% of bicyclist fatalities and 55% of bicyclist injuries occur at intersections. Signalized intersections are typically designed to accommodate motorized vehicles and pedestrians, but accommodations for bicyclists are rare. There are several ways signalized intersections can be designed to facilitate bicycle travel.

Bike Boxes
According to the National Association of City Transportation Officials (NACTO), a bike box is a “designated area at the head of a traffic lane at a signalized intersection that provides bicyclists with a safe and visible way to get ahead of queuing traffic during the red signal phase.”

A bike box is typically painted with an image of a bicyclist in white, sometimes with a green background, and places the rider in a conspicuous place in the intersection where drivers can see him or her.

Bicycle Detection
When intersections experience high vehicular volumes or speeds, they can sometimes be difficult for even experienced bicyclists to navigate. Bicyclists typically move slower than motorized vehicles and take longer to clear an intersection. Bicycle detection can be used to indicate when there is demand from a bicyclist to enter the intersection or to extend the green time on an approach to accommodate the slower speed of a bicycle. Vehicular loop detectors are calibrated to detect larger vehicles and do not always detect the presence of a motorcycle or bicycle, so bicyclists are detected using separate detectors.

Bicycle detectors are typically indicated using pavement markings, as discussed and illustrated in Part 9 of the MUTCD, to indicate the optimal position for the bicyclist to actuate the signal. Sometimes sign R10-22 is used to supplement these markings. Push buttons that bicyclists can press without dismounting are used in some cases, including some bike trail crossings in Connecticut where Rectangular Rapid Flashing Beacons (RRFB’s) are provided.

Bicycle Signal Faces
The current 2009 edition of the Manual of Uniform Traffic Control Devices (MUTCD) requires that traffic signal indications are arrow or circular. The MUTCD further states in Section 4D.07-F that, optionally, an 8” circular indication may be used for “a signal face installed for the sole purpose of controlling a bikeway or a bicycle movement.” Though they are not included in the current version of the MUTCD, bicycle-shaped indications are allowed under  Interim Approval IA-16.

This interim approval outlines the meaning of steady green, steady yellow and steady red bicycle indications; the allowable size, layout, placement and mounting height of the faces; and the allowable timing of the intervals associated with the bicycle faces. Under the Interim Approval, if an agency chooses to implement bicycle signal faces, they shall only be used where bicycles moving on a green or yellow signal indication in a bicycle signal face are not in conflict with any simultaneous motor vehicle movements, including right turns on red. Additionally, sign R10-10b is required for use with any bicycle signal face that is intended to control bicycles only, to reduce driver confusion.

Be sure to check next month’s Connecticut Crossroads for a Connecticut case study on bicycle signals from the City of New Haven.

If you have traffic signal systems questions, please contact:
Theresa Schwartz, P.E., P.T.O.E. – Traffic Signal Circuit Rider
(860) 486-4535 or theresa.schwartz@uconn.edu.