[zestyping]

This has to work even if network reception is weak or absent. You can't be certain that 100% of cars will receive the signal and get themselves out of the way in time.

[lwf]

Right, so don't use the network: broadcast a signed message on a band reserved for emergency services.

[tuatoru]

> This has to work even if network reception is weak or absent.

Or hacked maliciously.