This could be a lot of fun with some more polish! I think the core idea would be the risk/reward of going faster than other players. If you add some other mechanics that effect the way the player moves, then your skill ceiling could be very high! I would consider:

• Having cars partially slow down overtime from air drag, so players can use it when timing turns.
• Going faster than other players when you're right next to them could give you a speed boost, which could be weaponized by other players driving slower via air-drag to get people to launch off the road, but timed incorrectly would send the faster ones in the lead. (Or faster cars can just get boosts normally, obviously :P )
• Hills could be another way for players to control speed! A large downward hill could force all players to go very fast, or a series of small hills could slow players down as an obstacle when they need speed.

That's what I think could make this game really fun! I would also consider making it clearer at some point that going off the road has penalties (maybe make out-of-bounds ground have a certain pattern to it? Like a checkerboard or some stripes?) and make sure the windows don't Z-Fight with the buildings :)

Thank you for your game, and good luck in the Jam!