To unlock other cars, you need to find three keys per level. When you begin a level, it is a good idea to find all the keys, then complete the laps. It does not matter what you place when you are looking for keys; take your time, and complete the level. If you do not complete the level and found all the keys, do not worry, you still get the prize. However to go onto the next level, you must place third or higher.
