GM Milford Proving Ground, Michigan

This is one of the first and, still, the largest vehicular proving ground in the nation. It opened in 1924, and covers more than six square miles, and has 132 miles of roads, including a oval track providing close to a 4-mile loop; a banked circular track with a 4.5 mile circumference; a 67 acre “vehicle dynamics test area,” which is a large open paved area; a three-mile long straight track; a few multi-turn tracks and rough terrain courses; and crash and roll-over test facilities. It also has more buildings and staff than other large proving grounds, with as many as 4,800 people working out of its 142 buildings. GM operates a hot climate proving ground inside the Army’s Yuma Proving Ground, in Arizona. These are the two dedicated GM proving grounds in the USA (it has others in other countries).