I’ve seen the number of induction coils increase drastically over the years in The Netherlands. They are quite easily recognizable, as there’s typically a solar panel on a pole, that appears to provide power to the system.
Considering there’s a wide variety of vehicles on the road, surely each variant must have (slightly) different characteristics when passing over the coil; especially when in a specific place at a specific time.
And given that they are situated at highway exits (see picture) or after entrances, and road users unable to exit and enter elsewhere, it would be trivial to track the bulk of a vehicle’s trip.
This in context of ALPRs (in different forms) being in place at strategical locations (large junctions or at bridges or tunnels, and parking), and the address of vehicle’s owner; you’d be able to connect the dots, and end up with a pretty complete picture.
In the US at least, these are generally for monitoring traffic, both current congestion conditions and total traffic over time for planning repairs and changes to traffic pattens. This is the same basic technology that has been used at traffic lights for ages to determine if a car is waiting for the light.
It’s highly unlikely they could track an individual vehicle. These can measure the approximate mass of the metal in the vehicle, but not to a specific enough measure that it would be able to determine the difference between similarly sized models of vehicles, much less a specific vehicle. Mostly they just measure to make sure they’re detecting a vehicle vs metal trash or something that might be on the road. They are more sophisticated and lower cost to install and power than they used to be which is why they can now be used on moving vehicles vs previous iterations that only really worked for stopped vehicles near existing power infrastructure like a traffic light. But that’s about it.