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Comment by aftbit | Hacker News Reader

Don't forget about tire pressure monitoring sensors (TPMS). They operate around 433 MHz and each have a unique ID to stop your car from misreporting a low tire pressure from a car sitting next to you at a stoplight. They are required by law. While some use various techniques to avoid transmitting all the time (to save battery), many just blit out their ID and pressure values on a regular interval whenever the wheels are rolling. That means that whenever you drive over a bridge or toll gate that is properly equipped, you're feeding them enough info to uniquely identify you, even if they don't have a camera or any GHz radios.

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I have no idea where you live where they are required by law, but I've never heard of such a thing. They've never been required by law anywhere I've owned a car.

In any case, given they have batteries that eventually wear out, and older cars don't have them, it would still be more effective to use a camera.

Edit: even if they're required in new cars that doesn't make them mandatory on the road. It's not like all tires must be sold with TPMS.

The TPMS requirement in the US is ratcheted. Once you have TPMS on a car, it needs to stay on the car even if you replace the wheels. It must not be disabled or removed, and it must be fixed if broken.

Obviously, it is easy to flout these regulations as an individual or as a small-time mechanic. But there can be penalties if tampering or negligence gets discovered, the most common of which is failing to pass inspection. When I bought wheels from Tire Rack online in 2015, I had to either pay extra to have them equipped with TPMS or else attest that my vehicle never had TPMS.

The real purpose has nothing to do with surveillance but with consumer and environmental protection. If you buy a used car with TPMS, you should be confident that it works. And keeping it working increases the chances that people will keep their tires filled and their fuel economy up.

However, a new problem has arisen, which is that gas stations don't bother to fix their broken air compressors anymore.

I can find no mention of a TPMS requirement in my state. My older car has a malfunction in its TPMS and has for 10+ years. The repair cost I was quoted was ridiculous and I just periodically check the tire pressure with a normal gauge.

This vehicle has passed all required inspections for that entire time and the TPMS system hasn't even been mentioned in that context.

edit: I found the claim that TPMS was required interesting and a quick web search shows that 13 states in the US don't require vehicle safety inspections AT ALL.

It is not a state law, it is a Federal regulation under 49 CFR § 571.138 [1]. These requirements were fully effective for manufacturers and "alterers" as of 1 Sep 2008. However, yes, if your state doesn't require it (or doesn't require any inspection), then there's no way to penalize you as vehicle owner or reseller. Mechanics and aftermarket part sellers can still run afoul of USDOT though.

[1]: https://www.law.cornell.edu/cfr/text/49/571.138

I remember the rounds of media coverage about this when TPMS became required on new cars.

I have not seen any evidence that it is actually happening, though. Compare to this story where the reporter asked for tracking data and either received the data or a response confirming the data’s existence but declining to provide it.

Other data sources for tracking, like cell phone location or toll transponder pings, also have a public record of the existence of that data.

I’m not aware of a similar trail of proof-of-existence for TPMS data tracking. If you are, I’d be interested to learn.

You can monitor and track these as well with: https://github.com/merbanan/rtl_433

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