10 km/h/s isn’t even a hard brake. Real world co-efficient of friction is assumed to be 0.7 for old tires, upwards of 0.9 for new cars with anti-lock brakes, so braking at 20-30 km/hr/s should be possible without skidding. Which is why I wasn’t concerned about braking times in 6 second turns, because you reasonably can brake from 120 km/hr to a stop in 6 seconds. Now, the distance traveled was wrong, that’s true, but the rate wasn’t.
If we set realistic brake rates, the rest of the system should sort itself out - if you drive through a city at 120 km/h, even a hard brake at 30 km/h/s means you’re going to travel for 1 second at 90 km/h (11 tiles), 1 second at 60 km/h (8 tiles), and 1 second at 30 km/h (4 tiles)… so you only need 23 tiles of clear space to brake. Good luck with that.