This is great! I've been playing this (actively and inactively) for hours. :D
I did get to a point where all but one car got stuck (see screenshot below). The cars below the Delete Save button were glitching around on that corner. The car below the Save button was the only one still driving--others were simply still pointed at the side. I did try upgrading cars to see if different stats fixed the problem, but it did not.
HOWEVER, in logging in to leave this comment, the page reloaded and the cars are now unstuck. I'm not sure if it just loaded to a point before the stuckness or if reloading the game is a fix.
But regardless, excellent game! Very fun!