About an hour’s drive west of Detroit, Milford, Michigan, is the oldest and largest continuously operating manufacturer’s testing facility, General Motors Milford Proving Ground. Opened on September 25th, 1924, it started as a 1,100-acre property with five and a half miles of test track. Over the years, it has grown to over 4,000 acres and is home to over 150 buildings and 150 miles of road system, with 4,200 employees to operate all of it. Let’s review a brief history and some fun facts now that GM’s Milford Proving Ground turns 100 years old today.

Just as the first C8 Corvettes were being delivered to their new owners in 2020, GM was spotted testing the upcoming Z06 models at Milford.

Safety And Security At MPG

Milford has been the site of several safety developments over the years. Modern guardrails owe their roots to Milford. Of the 150 miles of paved track, about 130 miles of it have guard rails installed for safety during testing. The guardrail GM designed for Milford was adopted for use on US roadways. GM opened the first dedicated vehicle rollover test facility in North America at Milford in 2006.

Milford is a heavily guarded facility. You may think keeping over 6 square miles of land secure from unauthorized visitors would be difficult, but it’s in GM’s budget. Many prototypes are tested here that GM likes to keep quiet about, so the property’s perimeter is heavily guarded, and plenty of trees and fences keep prying eyes out. Also, only about 100 employees are allowed to drive most of the test tracks, and they have to earn a special license from GM.

Milford’s Features And Growth

One of the most significant structures that stands out in satellite photos is the circle track on the grounds. It’s a four-and-a-half-mile continuously banked circle course with five lanes posted with speed limits increasing towards the outer lane. The speed limit for the outer lane is 100 miles per hour. With the correct alignment and tire pressures, each lane can be driven at its posted speed without touching the steering wheel to simulate an endless “straight” road. The surface is paved in durable dolomite concrete for extra wear resistance.

One of the first test tracks had a long banked curve for high-speed testing. This heavily modified LaSalle roadster flew around this banking here in 1927 at over 100 mph.

In the center of the circle track is the Vehicle Dynamics Test Area, nicknamed the ‘Black Lake.’ It’s a 67-acre flat pad of blacktop for testing vehicle dynamics. It earned its nickname because of its large, flat black surface, causing birds to try and land on it over the years, mistaking it for a lake. At each end of the Black Lake are two half-circle tracks that vehicles can use to get up to speed before entering the Vehicle Dynamics Testing Area. There is also an area of the pad made of ceramic tiles for testing that requires lower friction, and another area where the asphalt is coated in Jennite asphalt sealant can be wet down to simulate slicker surfaces and other weather conditions.

GM has been known to bring in outside competitors for side-by-side testing, like Porsches and Ferraris. When the 2014 Z28 Camaro was nearing production, GM brought in a Boss 302 Laguna Seca edition Mustang. The Camaro was about 5 seconds a lap faster on the handling course.

Several additions and developments have occurred on the property over its century. In 2003, former GM Vice Chairman Bob Lutz pitched the idea of building a road course at Milford. The goal was a track duplicating several famous corners from racetracks worldwide to test performance cars. The course consists of 17 turns, with the primary focus being suspension testing with different elevation changes along its 2.9-mile length. Some notable corners are copied from the Nurburgring, where GM also likes to test its high-performance models.

Involvement In The War Effort

Milford was home to military equipment and vehicle testing for World War II. The US Army conducted over 1,500 tests on 900 vehicles while on Milford’s grounds between 1942 until the end of the war in 1945. All vehicles and armament used by the US Army during World War II were tested at the Aberdeen Proving Ground in Maryland, but the Army also needed GM’s Milford Proving Ground for endurance testing and testing equipment on different terrains.

Coming up the 25-percent grade gravel hill is an M26 Pershing tank. Both the Fisher Body Division of GM and Chrysler built the M26 tanks.

Milford Is Not Alone

Milford may be the GM’s largest, but it isn’t their only proving ground. A desert proving ground in Yuma, Arizona, was opened in 2009 to replace the older desert proving ground in Mesa, Arizona, which opened in 1953. It sits on 2,400 acres and features 40 miles of roadways on site for testing in the hot and dry Arizona climate. Just like Milford in the past, the US military has also used the Yuma Proving Ground for testing.

In the 100 years since it opened, there have only been eight fatalities on Milford proving grounds. In the summer of 2023, an engineer was involved in a wreck in a convertible C8 Z06 testing a suspension software update. Luckily, he survived.

A lesser-known GM proving ground, Cupuan del Rio, in southwestern Mexico, opened in 2006, primarily tests a vehicle’s HVAC systems. Even though HVAC was its primary focus, it also features a circle track and off-road courses. Due to security concerns in the region, it has been left mostly abandoned since 2011, with only armed security remaining.

GM also has proving ground in Europe through its Opel division. One facility is in Arjeplog, Sweden, where cold climate testing is done. Most facility’s test tracks are on a frozen lake, and temperatures are frequently below freezing. The other proving ground is ‘Testzentrum Dudenhofen,’ located in Dudenhofen, Germany. This is another facility GM operates through its European Opel division, which is just a two-hour drive from Nurburgring.

One of the many corners on-site at Opel’s Testzentrum Dudenhofen proving ground in Germany.

Astonishingly, a proving ground of this magnitude has been around for this long, and it looks like GM has no plans to slow down. It has provided us with improvements and developments in safety, technology, suspension, and braking, and last but not least, Milford has been a test bed for all the performance cars we hold so dear over that last century.