How to get L.A. Noire's Lead Foot Achievement easily

Are you having trouble getting L.A. Noire's Lead Foot Achievement? It requires you to maintain a speed of 80 mph for ten seconds. Running into too many other cars on the street? Here's an easy way of getting it done. Get a sports car or one of the fast hidden vehicles. A good one to get is he Cord 810 Softop; it's one of the hidden vehicles. Drive over to the Los Angeles river. I get there by Seventh street. I go down to the river and on top of the bank. I drive to one end of the river. Stay on the bank. I then floor it and travel down the river on the bank. No obstructions. You should get the achievement easily.