Rally car:
At Car Selection screen, hold R1+R2 until the race starts. Pick your car and color. Then you'll be racing the #15 rally car.
Lowrider:
Get all of the keys on Level 1. Press down at the Transmission screen for the lowrider.
Bus:
Get all of the keys on Level 2. Press down at the Transmission screen for the
bus.
Rocket Buggy:
Get all of the keys on Level 3 for a dune buggy with a jet engine on the back.
It hauls ass. Press down at the Transmission screen for the rocket.
UFO:
At Car Selection screen, hold R1+R2+L1+L2. Keep holding these buttons at the
transmission screen then press X. Press and hold Triangle until the race begins
and you should have the UFO.
Taxi:
Beat GP mode. At the Transmission screen press down to get a taxi.
Police Car:
Beat Circuit mode. At the Transmission screen press down to access the ultra-fast
police car.
Thanks to Revolution readers Kirk Huhn, Twista21, Brandon West, Dan O'Dea, TYRANT~KOB~,
Cameron Groves, Eric Hou, Devan Trammel-Fisher, Chad Anderson, Drew Moysan,
and Bradley Lyman!