In January 2007, Bob Lutz introduced the Chevrolet Volt concept car. A few months later it was given the green light to go into production.

Now the Volt, the production version of which will be launched in November 2010, is the No.1 priority within GM.

The Volt's platform, which is based on the global architecture that will underpin the 2009 Opel Astra, is set to go and there's a working mule running around GM's Milford proving grounds in Michigan using the drivetrain that will eventually come to market.

All that remains to be done is some tweaking to the interior and exterior appearance.

Frank Weber, the man in charge of the Volt, is candid about the work that still lies ahead. He says the real task is turning the Volt from a rolling test laboratory into a road-going car that will be robust enough to deliver a 10-year/240,000-kilometre life cycle.

In its current form, the Volt uses a small one-litre, three-cylinder flex-fuel engine (it can run on gasoline or E85 ethanol) to recharge the main battery as its state of charge drops. Unlike most hybrids, the engine does not drive the wheels. In the Volt's case, you start by charging the main lithium-ion battery by plugging it into the electric grid. When you leave for work in the morning, the Volt runs on the electricity stored in the battery.

This strategy would normally limit the Volt's driving range to about 64 kilometres. The clever part is that when the battery drains to a specific level, the gas engine fires up and begins to recharge the battery. The state of charge is not allowed to drop below 30 per cent and it never exceeds 80 per cent. This strategy protects the battery and delivers a longer life. The good news is that the battery/engine combination delivers a driving range of up to 1,000 kilometres from a small 45-litre gasoline tank.

When the Volt debuts there will be a number of changes to the body, the majority necessitated by the use of an existing platform and aerodynamic concerns. Bob Boniface, design director of the Volt, says the changes will not transform the concept car "into a Chevy Cobalt with a big battery." One of the biggest changes is to the headlight design; they are considerably larger than the concept car's, which improves night vision.

The need to reshape the front end, sharpen the rear fascia and add a spoiler to the production car were all driven by the aerodynamic side of the Volt's personality -- aerodynamic drag accounts for about 20 per cent of the energy consumed in an average vehicle. This directly impacts efficiency. In this case, it is the potential electric-only driving range that suffers.

According to the numbers, adding 182 kilograms of mass shortens the driving range by just 3.2 kilometres. Reducing the aerodynamic drag by a small amount adds as much as nine kilometres to the highway driving range. It is a delicate juggling act that will shape the car.

Until the arrival of the Volt, GM's environmental push continues with a few more traditional hybrids. In all, there will be eight gas-electric hybrid models on the road in Canada in 2008. The first front-wheel-drive application of GM's two-mode hybrid system (it is currently used in the company's SUVs and trucks) will hit the road in the 2009 Saturn Vue Green Line. GM claims it delivers a 45-per-cent improvement in the combined city/highway fuel economy when compared to the current non-hybrid Vue. A plug-in version of the Vue is also planned.

The Chevrolet Volt is one of the most intriguing vehicles to come along in a long time and it is destined to spawn many imitators because of its fuel efficiency -- a claimed average fuel economy of less than seven litres per 100 km. This number might not sound impressive until you explore the possibilities. If the driver's commute is 60 kilometres a day and they plug the car into the electrical grid between trips, the fuel economy will be zero litres per 100 km. For someone driving 300 km, the engine will be running for much of the time, so the fuel economy will likely be closer to the posted seven litres per 100 km. Somewhere between these extremes lies the actual economy -- a real-world average of around 4.5 litres per 100 km is entirely possible.