I suggest a large, wide highway to test our cars to the fullest. While sky Park City tests strength well, there aren't really many places to reach top speed, nor roads wide enough to allow high speed cornering to work, forcing you to stay at under 100mph much of he time. A wide, four Lane highway across the wright isles could solve this, featuring a long, straight bridge to the north runway that would more than allow you to Max out your speed, as well as corners of varying angles through the mountains to allow cornering at Max speed, and/or some drifting.