While being pursued by police, they'll often set up roadblocks ahead of you. You'll usually be able to hear them say they've set up a road block on the radio. You can see roadblocks on the mini-map, indicated by a red bar icon.
As you approach a roadblock, aim for one of the police cars in it and ram it. If you don't crash, you'll unlock the achievement. Aim for the front or the back, as hitting the middle usually ends up in a crash. Best done in cars with high toughness rating, or have reinforced chassis/impact protection equipped. You'll likely unlock this as you play through the game, since you'll hit alot of roadblocks anyway.