I have read about bikers fitting magnets to their bikes so that the sensors see them as a car and change sooner. unfortunately fitting a magnet to a car doesn't do much.
Most traffic lights here is sweden work well with this system. At night on a quite road you can just keep driving at normal speeds even if it is red and 9 times out of 10 it will go green just before you need to slam your brakes on (so as not to run through a red light).
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