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Comment by meowster | Hacker News Reader

In Houston, TX, USA, I noticed antennas placed over individual highway lanes. It turns out they track the Bluetooth signals from cars to determine traffic. They even have a message on their website saying people should be more worried about license plate tracking.

https://www.houstontranstar.org/faq/traffictech.aspx

On the OEM infotainment center in my vehicle, I can't even find a way to turn off Bluetooth.

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In one state I cannot mention, in Australia, there are at least 4000 of these things by the side of the road. During criminal cases its not unusual for a vehicles MAC address to be run through the database of collected data and matched to the vehicles location at a point in time. If the vehicle was also carrying correct plates then ALPR can be included. Prosecution gets to present a very pretty map with detailed timestamps.

I cannot mention the state because their presence is not disclosed publicly.

Yeah, I rewrote a system for a company that did this. If it makes you feel any safer, the original codebase was an error-prone mess written by an intern.

It’s not any more, but all it did was ping for MAC addresses at both ends of the stretch. I suppose the data could prove your presence, but it’s the presence of your car really. At least with Apple the MAC gets cycled now.

ok cool, did you leave a spare key under the mat so we can turn it off?

You know what you cant turn off? TPMS. I mean you can remove them from your car, but those little guys broadcast and with the right equipment you can track cars with them.

Yes. The IDs are unique, fixed, and easy to pick up. You have to broadcast a low-frequency signal first to enable them and they'll emit a signal. There are several projects on GitHub to pick them up, and I've successfully done it.

See: https://github.com/merbanan/rtl_433

Did you do anything useful with the data? I'd love to just have a raspberry pi scanning and logging them with timestamps to archive with video.

No, but I've been collecting all this data for a while and trying to see if there's a security business to be built around this. I do a lot of "RF" projects, so this is a natural extension.

Similarly in NSW Australia they had installed similar antannas on traffic lights/traffic light boxes. Iirc they would also track Bluetooth signals. Not sure they tracked the OEM infotainment stuff or just the drivers phone Bluetooth IDs

Can confirm that they do vehicles infotainment systems. NSW is also not the only state to have them.

Iteris (formerly Traffic Cast) is a company that does this too

https://www.iteris.com/products/travel-time

I just removed the bluetooth module from my car.

You remove the TPMS too?

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