Last week, the North American Car of the Year was announced. In a country still hooked on pick-ups, 4x4s and oversized gas-guzzling saloons, the winner came as something of a surprise. It was none other than the eco-friendly Toyota Prius — a relatively small Japanese hybrid combining electric and petrol power.

Victory for the Prius is symptomatic of the surging interest in and demand for “green” cars. And while the Prius’s win might come as a shock to some American drivers, one small French company has a far bigger surprise in store — a car that runs only on air.

The inventor, Guy Nègre, admits it sounds too good to be true but insists the car is a viable proposition for a non-polluting city car of the future. A former Formula One engineer, he has been working on prototypes for a decade, but last week said his company, Moteur Developpment International (MDI), will begin production of the Minicat air car this year.

The MDI minicat

“They are ideal for use in urban settings,” says Cyril Nègre, Guy’s son, who is in charge of the company’s technical office. “We don’t expect people to have a Minicat in their garage instead of a BMW, but as well as a BMW.”

The theory behind the car is simple. Instead of a petrol tank there are two tanks containing air compressed to 300bar — 300 times the pressure of the air around us, and slightly higher than the usual air pressure in a scuba diver’s tanks. When released from the tanks, the air expands, driving pistons in the four-cylinder engine, creating the equivalent of about 25bhp.

Weight is reduced because the tanks are carbon fibre rather than steel or aluminium, so the car tips the scales at just 550kg. The makers claim the 79-gallon tanks mean the car, which reaches 60mph, can manage more than 100 miles before being refuelled. And when it comes to filling up, there are two options. First, you can plug it into the mains, allowing its electric motor to compress air into the tanks. The drawback is that this takes about four hours. A faster option is to fill the tanks directly from a compressed air pump in only a couple of minutes, although it remains to be seen whether filling stations will ever install these.

MDI says the car will cost around £6,000 to buy and that running costs will be tiny. Driving for up to eight hours or covering 125 miles should cost just £1 in fuel, and servicing costs are similarly low: because there is no combustion, the oil needs to be changed only every 31,000 miles.

On paper, then, it has you itching to shout “Eureka!”, but what about on the road? MDI allowed me to drive the car, albeit only in the car park of its Nice factory, as it is not registered for road use. It wasn’t a good start: admittedly, this may have had little to do with the design of the car and more to do with my driving skills, but I found the gearchange incredibly difficult to handle — sticky like molasses. So much so that I managed to jam the car into reverse instead of second gear.

In the passenger seat, Cyril Nègre gave a few sighs and “Alors . . .” before diplomatically offering to change gear for me while I worked the accelerator and brakes.

We happily circled the parking lot at speeds up to 25mph. The car was not as loud as I expected it to be — it sounds like most other small engines, with none of the expected whooshing sounds of escaping air. ()

Gears aside, this rear-wheel drive car handles pleasantly, and I noticed how little different it is from a conventional car. Its interior is modern, but understandably sparse and simple in order to save costs and weight.

Since news of the air car spread through the motoring world, some doubting commentators have denounced the firm, saying its product is akin to the promise of the perpetual motion machine. But Professor Chris Wright, head of the Transport Management Research Centre at the Middlesex University Business School, says the concept is quite sound. “It’s perfectly respectable, it should work, and it should work better than any previous attempts to deliver a compressed air vehicle,” he says.