> (this is equivalent to speed cameras when the induction loop in the ground says that a car passed faster than the speed limit)

This isn't how many speed cameras work in Europe. They work by having a speed camera at location Y on the highway that snaps a photo of your car/license plate read, and then another one 5km down the road that also snaps such a photo and plate read.

If you average more than the speed limit in that distance between photo timestamps, you get a ticket mailed to you.

Due to the way it works, it's taking a snapshot of every single vehicle that passes each camera. How long that data is stored/etc. I suppose is a matter of how much you trust the government.

This system is considered better most of the time since it allows for brief excursions of the limit for overtaking, and doesn't just set up a situation where everyone slows down for the one known speed camera point (or slam on the brakes when they notice a mobile speed camera van on the side of the road).