Way back in the day (2010), I worked for a company using Bluetooth scanners to measure traffic speeds. We could get about a 500' range with custom hardware.

The real fun part at the time was that every Bluetooth device pretty much was always in pairing mode, and that MACs didn't rotate...

Eventually those both happened, but in ways beyond my comprehension (I worked on the software side), the hardware guys could still pick up the signals to track cars.

BLE transmissions go much further last time I experimented with them [0]. However the problem of anonymity comes into play since they frequently generate new MAC addresses.

[0]: https://news.ycombinator.com/item?id=38252566

> since they frequently generate new MAC addresses

This has not been my experience.

If you’re referring specifically to cars, you might be right: I’m not sure if they implement the MAC randomization most consumer products do, most of my testing was on those

> Bluetooth doesn’t have the signal strength beyond 20ft

Oh dear.

I think you will find a directional antenna can rather increase this by several orders of magnitude.

and 20 feet is not that short.

Those overpass things with cameras and transponders can definitely still pick it up within this range.

Plus like many have written, it's not even difficult to extend that range with cheap hardware.

I can almost assure you NYC subway does this.

Retail stores do too just fyi tracking you through the store. But it’s not pairing and it doesn’t have long range.