There is an 'express lane' in the center of the street where no cars run. This is a short ledge, only not present when a street intersects it. Sometimes it is obstructed by trees, but most of the time it is free for you to use. With a Cheetah, and only with a Cheetah (even an Infernus or a Stinger cannot match its speed in GTA Vice City Stories), speeding down the express lane southbound, you will slide off the lane as you pass the last street before entering Viceport. Passing it, you will go back onto the ledge, but this is slightly raised, and if you drive at it fast enough, you will hear a smashing sound, your Cheetah will be thrown into the air, flip once (if you drive at it at a straight angle) and land perfectly undamaged again (provided you didn't smash into another car).