Photo: Dan Burden

Guest blog by Sherry Adams and Don Costa

Why some signals are unresponsive to bikes, what the Sonoma County Bicycle Coalition is doing about it, and how you can be a part of improving signal detection of bicycles in Sonoma County

Why are many signals unresponsive to bikes? There are two basic causes:
1. The cyclist does not know the correct location to place the bicycle for maximum “recognition” (e.g. location of the sweet spot).  This is either because there is no pavement marking (icon) or the icon is not in the correct location. This problem is more complex than it sounds. The standard bicycle icon is much larger (5+ feet) than the actual sweet spot (often about 2 feet maximum). A bicycle wheel needs to be placed directly over the sweet spot. While most cyclists understand intuitively that the two heavy bars are meant for the placement of their wheels, at some intersections we have found that the sweet spot is under some other part of the icon.

2. The detector is set to a sensitivity level insufficient for detecting bicycles.

There are two sides to this problem. Bikes are being constructed of less metal and more carbon fiber. How easy it is for the signal equipment to detect a waiting cyclist (the “inductive footprint”) is a function of the amount of metal in the bike. As a result, bikes are getting harder to detect.

Most signalized intersections have a gizmo under the pavement (“detector loop”) in several places. The way these detectors are configured– for example if there are many loops connected to each other, and what sensitivity level they are set to– can contribute to the failure to detect bicycles.

Also, as loops age, they become unstable at high sensitivity settings. As a result, not all locations can be set to detect bikes without replacement of the detection system.

What is SCBC doing about it?

We’ve created the hazard reporting program where you can report road hazards including unresponsive signals. Thank you to the East Bay Bicycle Coalition for their ground breaking work creating a hazard reporting program over a decade ago; it was our inspiration.

The SCBC hazard reporting form is available on the internet at:

After you report an unresponsive signal, we will review what you posted and follow up with clarifying questions if necessary. What generally happens next is a site visit with equipment to find, mark and measure the sweet spot and evaluate the age and configuration of the detectors. This is done by the agency (Caltrans, county or city public works), by SCBC, or jointly, depending on the location. Often we ask the reporting cyclist to retest the signal. If the problem remains, we ensure the agency is aware of it and request replacement or upgrade of the detectors, placement or realignment of icon, or adjustment of detector sensitivity depending on the situation.

To date, we have received 52 reports representing 40 locations. We have initiated work on over half of these. At these intersections we’ve identified sweet spots and in some cases coordinated with agencies to increase sensitivity levels and move icons as needed. Only one intersection has been found to be unable to detect bikes until the equipment is replaced. We are happy to report that the agencies have been extremely cooperative.

What can I do to help?

1. If you use the on-line form to report unresponsive signals, please follow the directions carefully, accurate reports are a very important first step in the process. We may ask for your help in the follow up steps, especially returning to the signal to test any diagnosis we’ve made. Thank you for your patience as we work with our partners to troubleshoot and improve each reported signal. Progress is particularly slow in the winter as both temporary and permanent pavement marking require dry weather.

2. The signals program is one part of SCBC’s hazard reporting program. If you are interested in volunteering to help make the hazard reporting program a success, we’d love your help. Please e-mail us at (sorry, this is an e-mail based system and e-mail is required).

Some volunteer opportunities:

• Run the “paper” version of the hazard reporting program for people who do not use the internet. You need to create a paper form based on our on-line form, occasionally distribute copies to bike shops etc., and be willing to receive the paper forms and then enter the information from them into the internet. Estimated time commitment:

1-2 hours/week, some internet and e-mail access needed, though occasional access (e.g. through the public library) would be sufficient.

• Work behind the scenes passing on reports to jurisdictions. Training provided, time commitment is about 1 hour/week, daily internet, e-mail and telephone access needed during your “shift” (for example choose 2 days/week). You need to be willing to be courteous yet firm with public works departments, and have decent map skills to locate reports spatially.

• Be our computer wiz. Our on-line reporting meets the basic needs but we know it could be so much more. We dream of a map based program where cyclists can click on the spot on a map and the location report is generated in a backend file, along with an interactive on-line display of all hazards that have been reported with their status. There are some great models out there . This would require the most time in the beginning and would be a long term commitment to ensure the on-line system is maintained and remains functional.

• Be a cyclist! There are many reported hazards and we don’t have time or pedal power to verify which have been repaired. If we had a cadre of riders who volunteered to follow up on reports we’d be able to start tracking how many are actually fixed.

Sherry Adams is an SCBC board member. Don Costa is a transportation consultant with decades of experience in signal operations. We want to thank and recognize the dedication and assistance of the public works departments across the county who work hard to make our roads safe and in many cases are enthusiastic partners with SCBC in improving conditions for cyclists in Sonoma County.

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