Bicycle detection at traffic signals

Bicycle Detection at Traffic Signals Editor's note: Todays blog comes courtesy of Cheryl Schmitt, bicycle coordinator for Santa Cruz's public works department. Her submission hopes to educate cyclists about getting traffic signals to see them and go from red to green. Bicyclists often wonder if a traffic signal will turn green for them. The following information explains how traffic signals work and the best ways to be detected at signalized intersections. Types of Detection There are two main types of traffic signal detection in use today: video detection and inductive loop detection.
  • Video detection works with cameras that are mounted on the top of the traffic signals. The cameras recognize movement in each lane of traffic separately, including the bike lanes. When a bicycle is detected by the camera, the signal will turn green on the next signal cycle. The cameras are not used to detect red-light running or any other law-enforcement activity.
  • Loop detectors work basically like metal detectors. They consist of several “wraps” of wire set in saw-cut grooves in the pavement that connect to the traffic signal controller cabinet on the sidewalk. Loop detectors will detect any type of metal – steel, aluminum, or alloy. Since they do not work by pressure, the weight of the vehicle does not matter. However, the closer to the ground the metal of the vehicle is, the more likely it will be detected. If you are at a signalized intersection where you can see the saw-cut lines in the pavement, place your bicycle directly over a saw-cut line and you will most likely be detected.
Markings If an intersection has been paved over after the detector loops were installed, you won’t be able to see the saw-cut lines where the loops are. We have placed bike markings in these intersections to show you where to position yourself to be detected. Strategies for Getting the Green Light If you find that you are not being detected after waiting for a very long time, you have four short-term options:
  • Position yourself in the center of the travel lane and directly behind the stop bar;
  • Position yourself on a different loop;
  • Wait for a motor vehicle to drive up and change the signal;
  • Use the pedestrian push button.
Your best long-term solution to a bicycle detection problem is to contact the Public Works Department and report it so that it can be tested. Oftentimes, a minor adjustment at the traffic signal controller can fix the problem. Problems (at traffic signals countywide) can be reported to the Santa Cruz County Regional Transportation Commission by submitting a Bike Hazard report. Find it on their website at or call 460-3200. They will forward your report to the appropriate Public Works Department.
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