It probably wouldn't be feasible, mostly because if it got smashed by a car, a fairly potent alpha emitter would possibly be released, which is an ingestion and inhalation hazard. The radioisotope usually used (Pu238) is also not produced very much right now so it's in short supply. You make it in special Neptunium-237 targets inside nuclear reactors. In terms of power you can get well up into the hundreds of Watts fairly easily but it can get big. Here's the one used in Mars Curiosity rover [1].

[1] https://en.wikipedia.org/wiki/Multi-Mission_Radioisotope_The...

People talk about using isotopes from nuclear waste for this kind of thing a lot but they're usually considered too expensive.

I wish it was easier to get your hands on refined isotopes. I believe it'd spawn quite a bit of interesting industrial research that's being held back right now. A lot of this waste is a nuisance, but I believe if it was easier to get access to it, we'd see someone start to solve the waste problem.

Definitely agree. I didn’t know about the supply/production issue, though. Thanks for that.

My answer was of course a pure hypothetical, focusing on the pragmatism in a world where the safety issues were non-existent, presuming demand would drive supply.