Or just attend to the personality of the individual dog and train them accordingly. I personally have to harness one of my dogs in the car to make sure she doesn't get into shenanigans because she absolutely would jump out an open car window if she saw a motorcyclist (her one big trigger), but the other is seven years old and has been riding loose with a fully opened window to hang his head out his entire life. I pass the same three rabbits grazing in my driveway every day and he doesn't care about them. He can see another person in a car next to mine at a close enough distance for them to reach out and pet him if they wanted, and he will not attempt to jump over to them. He's very afraid of heights because he's epileptic, even small heights, so I'm zero percent worried about him jumping from the height of the car window to the ground.

I also live in the sticks, and I know a ton of people who ride their dogs around in open truck beds or even on a flat bed with no sides on it (saw that yesterday, dogs riding on an open trailer flat where they could have jumped off or rolled off or been thrown off from any angle).

Not saying I approve of that because I think putting your dog in a truck bed where you can't even supervise or correct him if he shows inclinations to act up is dangerous, but these weren't puppies doing this. These were old dogs that had been doing this their entire lives. And I know a lot of country folk that do it.

So apparently not every dog is stupid enough to jump out of or off of a moving vehicle. My older dog is intelligent as fuck and would never consider it, I would stake his life and a month's worth of paychecks on it.

My younger dog is just smart enough to think she could feasibly get away with it if she tried.