[qbasic_forever]

You're thinking about this the wrong way. Don't optimize for the car behaving perfectly--like you said it's impossible for you to verify this. And even if you could formally prove a car is perfectly behaved, you are driving on streets with other cars and other unpredictable people who could just as easily crash into you.

Optimize this problem by buying a car with the best safety rating. This is something that can be objectively measured, both in crash testing/labs and from reviews of real-world crash results. Expect that a crash could be inevitable as it is totally out of your control. Optimize for the best odds of surviving a crash without issues.

[Yujf]

Problem is that if you do that, you make the road less safe for everyone else

[vel0city]

Only if you're then also willing to go up a size in vehicle. You can still choose more or less safe vehicles from within the same class. A 2022 Corolla is way safer than a 1998 Corolla, that 1998 Corolla is safer than a 1966 Corolla, etc.