Lot of comments here are accusing the "hackers" of negligence, but do not forget the writer, camera crew, and editors of WIRED were fully in control of the demonstration. This happened in the context of journalism, not security research. Blame WIRED if you think they screwed up, not the folks behind the computer.

It was up to WIRED to ensure the safety of the demonstration, and evidently they failed given this passage,

After narrowly averting death by semi-trailer, I managed to roll the lame Jeep down an exit ramp

Seems to me they should have at the very least had a chase car trailing the demo car with a sign, flashing lights, or flags to alert nearby drivers.