Tomb Raider III Cheats

Go to the last of the obstacle (the one with the zip line). Climb up to the standing area and walk to the top right corner (facing the shooting range). Turn diagonally to the boundary wall on your right, jump straight upward and press the action button.

If you do it correctly, Lara will wind up on top of the obstacle. Jump onto the red square in the air next to you and from there, jump onto the roof. From the roof, you can jump into the racetrack without the key.

Note: you may need to adjust a bit when facing diagonally to the wall to get this trick work.