Large concrete areas to test builds?

Looking for suggestions on where I can test out my MoCs. Have been using the road outside my house (seldom get traffic, and can see cars coming from a long way) but the asphalt is difficult to drive steady on. Small bumps cars dont notice tend to bounce my cars. My suspension work is honestly minimal but even when attempting to compensate its not enough. I need a large open area of concrete to conduct speed tests. Any suggestions? Im located in the US if its helpful. Thanks! submitted by ...