Hijack
From Halopedia, the Halo wiki
Summary
The Carjacking Medal is awarded for stealing an occupied vehicle from an opponent. It is availible in all Multiplayer gametypes where a vehicle is availible and has a Bungie difficulty rating of 2 (out of 10). It is represented by a cross with a U-turn sign on it. After you board a vehicle a message appears on your screen that says: "You boarded an enemy vehicle".
