5/10
it's a real shame about the vehicle physics issues, because this game has a really nice vibe! the controls offer an interesting learning curve, and I did start to get into a groove by the end, but the awkward collisions and random stops prevent a true flow state.
I definitely think you should work on this a bit more and fix those bugs if you're up for it, because there's a lot of potential for arcadey fun. Maybe you could even reintroduce more elements of the zombie apocalypse that I assume got cut due to time constraints.