Warning: I can guarantee someone will post about how dangerous it is to PE and drive at the same time. I will say that you can’t and should not use both hands to PE while driving but there are certainly some simple exercises you can do while driving safely.
I have an hour commute from my house to school so I do try to get in some stretching but I’m not sure it is worth it.
First of all, you have to wear certain clothes that allow you easy access; meaning specific underwear (or none at all - which is okay but not feasible all the time). On top of that your pants/shorts should be appropriate though it would be possible to change once you get to your destination.
Secondly, as I mentioned before your exercises are limited. I suppose you could stretch, fowfer (almost), kegel is a great option of course, and I suppose if you had a clamping device that was very, very easy to release and re apply you could make that work but I can just as well imagine that being a really bad idea so just be careful.
Also, sitting in a car seat is different than sitting on a couch, bed or chair. You become limited in how you can stretch and with fowfers you cannot easily keep the pressure on the stretch if you have to use your legs to shift/break/accelerate.
Overall, not the best way to get it done but if you have no other options you could do SOME-thing (one-hand stretching and kegels) to PE. Of course this is just my opinion from experience. I would be delighted to hear other peoples experience and ideas.