Behind closed doors at a proving ground, a new car may find itself ageing ten years in 20 weeks. Paul Markillie goes along for the ride ...

From INTELLIGENT LIFE Magazine, Summer 2011

We complain about the state of the roads, and this one is making my teeth rattle. The car is only going about 30mph but the wheels are frantically drumming up and down over uneven cobblestones. It is a tough one for vehicle integrity, says Miguel Fragoso, using engineer-speak to describe a road capable of shaking a car to bits. Yet this piece of road will never be resurfaced, because Fragoso likes it just the way it is. 

He is managing director of the Millbrook Proving Ground, a sprawling 700-acre site hidden away in Bedfordshire behind security fences and high embankments. This is to prevent the car-world paparazzi snatching pictures of the new models manufacturers bring to test here. Even the lens on my mobile phone has been covered with a tamper-proof security seal. Not that the cars here look pretty. Many have not been washed for weeks and are covered in layers of dirt and dust. That too is deliberate.

Millbrook is a sort of automotive time machine. A shiny new model arrives, and after about 20 weeks it will have been exposed to the equivalent of ten years of severe weather and wear-and-tear comparable to being driven 160,000 miles or so—the lifetime of a typical car. Day and night it will have been driven fast and slowly, up and down hills, around twisty corners, through salt-water baths to accelerate rusting and along gravel roads to pit the paintwork. It will also be frozen, baked, soaked in water to reveal leaks, and bounced along the notorious Belgian Pavé, the one-mile circuit we are on. This is built from blocks of paving with rough sections and random depressions. The pounding it gives the suspension is so severe that after about five laps a car needs to be driven into a trough of water to cool its dampers down. 

Carmakers also test future models on public roads, often disguised with stick-on panels, and take them to harsh environments, including roads within the Arctic Circle and deserts such as the Mojave in California. But proving grounds like Millbrook allow a lot of tests to be done in one place and in repeatable, carefully measured conditions—including the ultimate wrecking exercise: strapping in dummies and smashing the car into a steel wall to establish its crashworthiness. 

During the accelerated ageing, engineers take the cars apart and examine them for worn and broken parts. This allows carmakers to tweak designs and change production methods to prevent failures which would be costly for them to fix under warranty, and embarrassing if vehicles have to be recalled. Such testing processes have helped carmakers to raise their quality, resulting in warranties getting longer. Some engine guarantees have gone from three to five years and more; anti-corrosion warranties now sometimes extend beyond ten years.

The engineers are not just looking for wear and tear. Among the most irritating problems for motorists are noise, vibration and harshness, known as NVH in the business. Shaking things up on the Belgian Pavé is one way of testing NVH, but there are others. Cars undergo extreme temperature variations, for instance. Jump in a car on a freezing morning and the temperature could be -10°C. Five minutes later, with the heater blasting away, the temperature of the dashboard could have soared to 30°C. As different materials expand at different rates when heated, this can cause niggling rattles to occur. Carmakers do not want their precious models to gain a reputation for rattling every time the heater is turned on.

Nor would they like them to be known for sloppy handling. So setting up the suspension and steering to cope with different surfaces is also a big part of the job. One of the most demanding courses on which to test vehicle dynamics is Millbrook's picturesque hill route. It swoops up and down hills and around tight corners, just like an Alpine road. It is so realistic that film-makers use it; when James Bond needed somewhere to flip his Aston Martin over seven times in Casino Royale, this was where Daniel Craig and his stunt doubles headed.

At other times the 60 or so drivers working at Millbrook need to test a car as if on a very long straight road. This is provided by a high-speed circuit built in the 1960s when General Motors began developing the centre, which is now run as an independent company. The high-speed circuit is a two-mile, five-lane circular road that is banked. I have driven around here before, as occasionally manufacturers bring people to Millbrook to test their cars. But I never really understood the physics involved. Being banked and circular, each lane has what is called a neutral-steer speed at which the forces acting on the car are the same as if it is going in a straight line. So, as Miguel demonstrated in lane four with its neutral-steer speed of 75mph, it is possible to take your hands off the steering wheel. Accelerate harder, and the car moves on its own up into lane five, where the neutral-steer speed is 100mph. This track allows the miles to be piled on a car but with a constant force acting on the suspension. So, for instance, if you wanted to drive 500 miles at 100mph in a straight line—which is impossible on any public road, anywhere—you would just need to do 250 laps of this circuit. The track is used for testing things like durability and engine cooling. 

The straightest road at Millbrook is a mile long and level to within a fraction of an inch. It is used to test acceleration and braking times. There are other courses designed to represent different road surfaces, with nasty obstacles like steep kerbstones and some of the meanest pot-holes I have ever seen. One of the reasons for driving into obstacles like this is to check that the impact does not accidentally trigger an airbag. 

My interest, however, is captured by the menacing off-road course where signs warn of hazards like Mortar Holes and The Sandpit. We swap Miguel's car for an old Schwarzenegger favourite, the civilian version of the Hummer. I've always reckoned this is a bit of a softy compared with a sturdy Land Rover Defender. But when Martin Newbery, a driving instructor at Millbrook, takes the wheel and plunges us through muddy, slippery, deeply rutted tracks with near-vertical hills, steep descents and water-filled pits, he starts to change my mind. 

I have a go too, and conclude that there is no substitute for the rough and tumble of a road-test (preferably in someone elses car) to discover a vehicle's true strengths and weaknesses. And the Hummer is rather good, if you don't think about the miles per gallon. If Britain's roads get any worse, which they surely will given the current belt-tightening, General Motors should find a way of reducing its thirst, and put it back into production. 



Steer clear of bumps Driving over cobblestones or speed bumps takes its toll on the suspension. As do pot-holes.  

Keep calm Aggressive driving means greater wear-and-tear.

Get a jet-wash Rust gets worse when roads are salted, so jet-wash under the car in winter. 

Polish pockmarks Stones thrown up by other cars chip the paintwork, leaving small pits which can rust. These need to be repaired or have polish rubbed into them.

Don't make a splash Water can wreck electronics, and even engines, so take big puddles slowly.

Do your homework Even 4x4s can come to grief when you head off-road. Know their limits or get off-roading lessons.


Paul Markillie is innovation editor of The Economist. His last cars column was about the lure of campervans.