According to GM, Milford Proving Ground has 150 buildings, and “test road surfaces equivalent to over 150 miles of two-lane highway, providing a wide variety of road-testing possibilities that ...

So GM has added a 3.6 mile section of track to its Milford Proving Ground facility in Michigan, a section which directly mimics the (in)famous North Loop, with 20 turns and 98 feet of elevation ...