Say I'm talking about a car that has less of a tendency to crash than other cars. It is the opposite of a "crash-prone" car. But it isn't "crash-proof" either, in that you can crash it if you try hard enough.
both "-proof" and "-resistant" have connotations of being able to withstand a crash without taking as much damage as might be expected rather than being less likely to get into a crash in the first place, so I'll suggest "-avoidant". Although I'd probably recommend using it as in
because saying "the car is crash-avoidant" just sounds funny to me.