To unlock this Achievement you need the Vehicle Takedown Perk which is unlocked after completing 1 Race, you can find the Race Quest start point near the first village.
Once you have the Perk either Join a friends game or host one. Find a Vehicle and have your partner drive and look for an enemy Vehicle. Once you find one pull alongside it and you'll get the option to perform a takedown. Simply hit
and you'll leap from your car to the enemies and perform the takedown.