All traffic lights that aren't sequentially timed, use ground loop metal detection. Those lines cut into the concrete/asphalt forming a rectangular shape are where the loop wires are inserted into the road. When a large piece of iron/steel is placed over it (like a car engine) it changes the inductance measured on the loop and triggers the light circuits. The problem we have is that aluminum/plastic have no effect on the loop. If the loop is too deep, the little bit of metal we do have is not enough to trigger the circuit. Stopping on top of the cut lines or putting your kickstand down on the line can sometimes get the metal close enough to be detected. But sometimes the sensitivity of the circuitry isn't enough for a bike to ever trigger the light.