Yes and no. Let's say everyone drives compact cars, then my risk level -- completely made up number -- is 20. However, if everyone's driving para-tanks while I keep driving my compact car, then my risk level rises to 60, due to aforementioned physics. Now, if I join everyone, then my risk level falls to 40, so I'm safer. But compare to the initial case, I'm still less safe. Hence the prisoner's dilemma.
I’ve been downvoted over this before but really we just need weight limits on cars. Efficiency is pretty closely aligned and we seem to regulate that just fine.
