Four thousand acres of Michigan. An electrical substation, a wastewater plant, fire crews, and a medical centre that never shuts. No number plates on the cars. And, of roughly 81,000 salaried employees at the company that owns the place, fewer than 200 are cleared to drive its fastest roads.
The site is General Motors' Milford Proving Ground, which opened on 25 September 1924 and is the oldest dedicated vehicle testing facility in the world. It sits in suburban Michigan between GM's hubs in Flint, Detroit, Lansing, and Pontiac. GM describes it as rarely open to visitors.
