A small, simple, but solid little wroom-wroom. :)
I like how camera zoom depends on the velocity. I would make it "inert", so that it does not zoom in so abruptly (i.e. instantly) when you suddenly slow down due to hitting another car, something like:
zoom = zoom * drag + targetZoom * (1 - drag);
in each frame (assuming consistent framerate), where "drag" would be a positive constant between 0 and 1 (perhaps closer to 1, for a more noticeable effect, e.g. something like 0.8) and targetZoom would be the calculated velocity-dependent zoom.
Other thing I would add is an additional key for throttle (AFAIK, PICO-8 supports two additional game inputs besides the direction input). As already pointed out in a previous comment, it would be better for playing with a gamepad (which I initially intended because it is more relaxing, but quickly decided against it, noticing the difficulty with confusing controls).
Now, I wrote a lot about these two things, but they are really minor issues (it is me who sometimes knows not how to put some thoughts in not too much words) and overall this is a great work, congratulations! :)