This one is a definite "maybe". We have received feedback that magnets as small as our D84 discs have successfully triggered traffic lights, but we have also received reports that magnets as large as our DX8C have failed to trip similar traffic light sensors. It seems that there are different types and different sensitivities of traffic light sensors, and magnets will trigger some, but not all of them. If you have any feedback or good information on this, we would appreciate an email with any details you may have.