I don't have construct under my hand at the moment, but somewhere among the behaviours should be a rotate property which you could set to "no". Though I am not sure you have it under car behaviour.
If not, you could make the player sprite invisible, then add another player sprite over it and pin it to invisible one, with only the position pinning set in events. Thus the invisible one drives like the car, behaves like the car, but the visible one you attached on top always faces same direction. Sorry, bad english. I hope it helps.