By John Allen, CRW Safety Coordinator

This article is especially for ride leaders.  It describes a problem which you may encounter as you plan a ride, and potential solutions.

Many traffic lights are triggered to turn green by metal detectors buried in the roadway. These do not reliably sense bicycles. In another article, I showed how you can try to make these work when riding alone.

As you vet a ride, you need to check whether the metal detectors work. If you are riding alone, the testing can unfortunately place you in a scenario where you must either 

• wait for a car to roll up behind you and trigger the signal, 

• or cross lanes of traffic to the side of the street and push a pedestrian beg button (if there is any)

• or cross the intersection against a red light. 

The problem is most troubling if you are away from the right side of the street – going straight where there is a right-turn lane to your right, or turning left from a dedicated left-turn lane. 

The video below shows my own experience of this problem. I positioned my wheels directly over the wire cuts visible on the road surface, the best place to trigger the detector, but I waited till the third time traffic from my direction got the green light before a car came up behind me and I got a green left-turn arrow. 

When riding in a group, two or more bicyclists can position themselves to strengthen the signal at the metal detector. So, I recommend riding with a friend to check this out as you vet your ride. 

The detectors which are most likely to cause problems have the wires in the pavement in simple rectangles, like those in my video. Bicyclists who approach the detector double file and place their wheels over the wires on both sides will almost always trigger the detector. To the detector, they look like one bigger vehicle. It may help to reach across and hold hands with your companion. 

For this strategy to work during the ride, participants need to understand it, and to arrive at an intersection two or more at a time. Instruction can be in the pre-ride talk, Ride with GPS cue, or ride information online. Teamwork works best with a led group, where the leader can direct participants where to wait at each intersection. It is tougher on a show and go ride and hardest of all on an invitational ride such as a CRW Century, where many participants are not club members. 

If the detector has a wire cut down the middle as well as one at either edge, it works best to place the wheels directly over the middle wire. This will usually work for a single bicycle. 

Carbon-fiber wheels with folding tires (no metal) will not trigger a detector, sorry! I have suggested that carbon-fiber rims should have a thin loop of wire running all the way round. You could arrange this yourself, if you care too. It has to be a complete loop, connected into a circle. Maybe someday someone will sell conductive rim tape, but I’m not holding my breath. 

You might also route your ride to avoid the problem. It will rarely occur with right turns, as right turn on red is usually legal. It is less likely when approaching an intersection on a busy street than a quiet one, because a car is more likely to trigger the detector.  But CRW rides are more usually on a quiet road crossing a busy one. We like those quiet, scenic rural roads!

Left—a detector loop with a center wire cut. Upper right: a video detector. Lower right: marking sometimes seen to indicate where to wait – though not always correctly placed. Image credit: cyclingsavvy.org.

Increasing numbers of intersections are being equipped with video cameras for vehicle detection, and you will recognize them looking down toward you from overhead signal masts. These are generally reliable to detect bicycles, except that you may need to tilt your bicycle and aim the headlight up at the camera at night. CRW generally does not run rides at night, but I might as well tell you anyway.