Tsavo Highway is the fourth campaign mission of Halo 3. Upon completing it on Normal, Heroic, or Legendary the player will unlock The Road achievement, worth 20 Gamerscore.
This level introduces new drivable vehicles to the player and is meant to allow a player who may be unfamiliar with the game to have some time to get a feel for the controls and physics of vehicles.
After successfully evacuating the upper area of the Crow's Nest base, John-117 finds himself in an underground garage containing multiple Warthogs and leads a group of Marines out of an underground tunnel. He then leads the surviving marines towards the town of Voi. A Pelican drops a pair of Troop warthogs and one regular M12 (with M41 LAAG). After fighting his way down the highway, through many Covenant troops, SPARTAN-117 breaches the barrier blocking the path leading to Voi and the ancient Forerunner artifact, buried beneath the Earth's surface.