First create a goal near an OB. Set the goal to driving mode and place the position on the ob so when u start the goal you will go out of bounds straight away.
Now play the goal and you should warp as you normally would in an OB. Now end the goal and get into walk mode and jump into the ob and just before you go out of bounds goto the menu and press restart goal. If you timed it right the goal should restart and you will be in the car in/on the OB.
You can do this in most levels with a car and a OB area. Also once you have got into the OB you can drive to other OB's in the level without warping.
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