Crackdown 2

How I got this was to use a magnet grenade to stick a light vehicle to the underside of a bridge, that way it will never touch the ground.

hope my suggestion helps

I figured I'd add to the 2 guides already here and try and make it a little simpler.

What you need -
1. 2 players
2. 2 mag grenades. Yes you only need 2.
3. a place that has a metal bar or piping that goes over head.

My friend and I used the oil refinery just by the bridge that goes over to Agency tower. Seems to be a traing facility for the cell. There's lots of explosive barrels some freak targeting stand ups and re spawning cell soldiers.

Tag one mag grenade to the over hanging pipe and one to a vehicle. The vehicle size doesn't need to be small. We used one of the big trucks. One person shoots the the other, do it until the chievo pops. Remember to lock on with your left trigger so you are shooting at the vehicle. The vehicle WILL NOT come loose if thats a fear, I think it takes and act of god to dislodge it.

Hey Gamers Quick way to Achieve the Achievement. I created this video for you, I hope this helps you with the Achievement, Probably The EASIEST method

You and a friend both need to have the "UV Shotgun". Find a very tall & wide wall, one player should pick up the car and throw it against the wall (This is so that the car stays stationary and you don't have to run for it.) Now once it has been thrown against the wall and is sliding down take turns shooting it with the "UV Shotgun's" (While keeping it off the ground of course.)