I do love me some Crazy Taxi nostalgia. But the controls here felt very difficult. It felt like I was constantly stopping when I didn't want to, and unable to stop when I wanted to. My advice if you want to expand this game further: ignore all physics-based movement implementations, just stick the car model on a CharacterController, and use CharacterController.Move. Tweak it so you can stop on a dime, and I can't remember if CharacterController does friction during collisions or not, but if it does, turn that down to zero. You want to slide along walls like an ice cube, only to brake to a dead stop the instant you take your finger off the key.
(Later, add juice during a polish pass, like sparks flying off the walls during a scrape and the car bobbing in place while a tires screech plays, so it feels like there's physics, even though there is not. 90% of video games is knowing what to simulate and what to fake-- and on some level, it's all fake!)