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.
With the exception of the highest heat levels, there's usually some conviniantly placed gaps that you can drive through. Slow down if you need to, and drive through the gap without hitting any of them to unlock this achievement.