A hidden vehicle demo map named "vehicledemo" can be found in the "\ut2003\maps" folder. Play it and hit the switch on the ground. A giant car that shoots rockets will fall from the sky.
Note: Type use at the console window when standing next to the car. You will be able to drive it.
After you have entered the vehicle, use the add bots code to add some bots to the map. Get close to them while driving the vehicle and it will auto-target them. Press [Fire] to shoot the vehicle's weapon at them.
If you enable the freecamera true code while driving the vehicle, the frame of it will disappear and you will be driving a set of wheels with lights.