It's a traffic priority system many of the 7 cities implemented years ago and is based on flashing pulsed NIR light, it's what makes the lights suddenly go red for you, and green for the cop/ambulance. The newer versions are GPS based, but last I checked (the budget is accessible online, none have upgraded). It's been federal law not to tamper/abuse this for a while, did it ever make it to the general assembly? I've got some new IR arrays I want to try out but I don't want a 30k dollar fine or 2 years in jail.