Driving A Destroyed Vehicle
From Halopedia, the Halo wiki
You need two people to do this. First go to any level or multiplayer map. To ride a destroyed vehicle first some one has to stand next to a damaged vehicle. Then some else has to stick the person next to a vehicle with a plasma or spike grenade. As soon as the person sticks the other person the other person has to get in the vehicle and the other person has to board the person in the vehicle. The grenade will kill the person in the vehicle but not the person boarding it. The vehicle will explode (if you damage it) and some one will be riding a destroyed vehicle.