You could set invisible "guid-sprites" wich are setting waypoints .. I don't really understand why you need buildings in a derby-car-game .. isn't this a big place where car's are ramming against each other hoping to not become destroyed? ^-^ .. otherwise .. you can just set waypoints like in Here
(the capx was made by YANN).
Than you can add a distance(player.x,player.y, enemycar.x, enemycar.y) event that says "set angle towards player" or something like this .. and to avoid the buildings you have the waypoints
A capx would help of course =) ..