The most common use is LIDAR – LIght Detection and Ranging, which is similar to RADAR except instead of using a wide microwave they use a tight laser emitter. The laser beam is tight so they can single you out in traffic, has much further range and is less prone to error.
Everyone has seen traffic cameras , they pitch them as part of a “safety program”, but they’re in fact illegal in many cities and states because they cause more accidents than they prevent. Still, they continue to use them against court order because they product SO MUCH income that local law enforcement still turns a hefty profit after paying court fines.
This is one of many examples that prove most traffic enforcement is about revenue, not safety.
Automatic plate reading can be convenient when pulling people over; it automatically and quickly pulls the plate data so that when an officer approaches the vehicle, s/he has a better idea of what they could be dealing with. This in and of itself has no direct privacy connotations – the driver is assumed to be stopped for cause, and if not then that’s another subject.
The picture at the head of this article and at right are examples of mass readers, where the officers’ car is stationary – there may not be anybody in it since it’s fully automated – but every car in the area has their license plate scooped up and fed into the system. On the surface it provides information so that if there’s a riot after a presidential election, for example, law enforcement knows who was in the area. The problem is that it ditches the fifth amendment because people can be (and were!) arrested in a dragnet and then had to prove they weren’t involved from inside a jail cell.
These records have also been used successfully in private court cases, such as when a wife wanted to confirm her husband was cheating on her. She had the records pulled and presented in court.
Here is a view from the other perspective: https://netchoice.org/lprfacts/
Does the end justify the means? Not when it’s ruled unconstitutional: https://digitalcommons.hamline.edu/cgi/viewcontent.cgi?article=1054&context=hlr
Automatic plate readers pull the Department of Motor Vehicles records including name and address, so it makes it easy to send drivers bills for tollway use. It also provides a great deal of data on who uses tollways and how often, and makes “peak time” billing possible; just tell the computer how much to charge people based on times of day and the bill arrives in your mailbox or is taken directly from your account.