[_Nat_]

Alternative hypothesis, for the sake of example -

Someone's just really be into practical jokes. Possibly the neighbor whose alarm keeps going off, or possibly a third-party who found an easy way to trigger the alarm.

But, my first thought on this thing triggering when he backs up is a rear-view sensor that uses a projection to get data. Apparently the 2018 version of his car has radar sensors that go off when backing up (https://www.subaru.com/engineering/safety.html):

> Rear Cross-Traffic Alert uses radar sensors to help warn you of traffic approaching from the side as you are backing up, utilizing an audible warning and flashing visual indicators in your side mirrors and Rear-Vision Camera display

[DonHopkins]

I wonder if backing up would set off other people's radar detectors.

Reminds me of "Trolling for Taillights"!

http://www.cs.cmu.edu/~hgobioff/public/random_stuff/traffic