Or by doing even a slight amount of encoding of the IR signal. Transmitting a single byte as a key (set by region, same as fire dept. elevator keys) would be enough to prevent people from using their TV remote controls or whatever to trip the preempt sensors.
That being said, this is kind of a non-issue already, I have heard a story about someone abusing the preempt sensors like 10 years ago and never since then. Maybe there already exists an encoding scheme.
Anecdotal of course, but in my 20 years of driving I've never once seen a vehicle activate the red light override sensors that wasn't obviously a legitimate emergency vehicle.
IMO a huge majority of people realize how illegal it would be to mess with these things, and the risk/reward is very low. Anyone who would take that risk would probably just run a red light instead.
