Coastal Highway
Coastal Highway is an Achievement in Halo 3: ODST. It is unlocked when the player completes Coastal Highway at least on normal difficulty in Campaign Mode and unlocks the map Last Exit for Firefight. It is worth 50 Gamerscore.
It is represented by an olive circle, with the Marathon symbol imprinted in it, with a Waste Disposal Elephant (otherwise know as an Oliphant) in front of it.