Hazardous HangtimeG 10

If you take the Agency SUV or go-kart in the elevator to the top of the big skyscraper in the Shai-Gen area, you can then drive/carry your vehicle out onto the roof of the building. Once out on the roof, get in your vehicle and drive off the roof toward the street below, which should cause the achievement to unlock once you land. It's also possible to have another player throw your vehicle off the roof in co-op mode.