It's difficult to overstate the importance of the new BMW 3 Series. Globally, one in every five BMWs sold is a member of the 3-Series saloon family.

So to make this sixth-generation version even more successful BMW has concentrated its efforts on reducing emissions, with 24 versions emitting less than 120g/km of CO2. Compare this with just a handful of versions of the soon-to-be-replaced Audi A4 and Mercedes C-Class and the forward step looks all the more impressive.

This is embodied by the 320d EfficientDynamics diesel model with emissions of 109g/km of CO2 and best-in-class fuel consumption of 68.9mpg. However, this version's, low-drag aerodynamic body, stop and start and low-drain electronics are now fitted to every 3-Series in the range.

For the first time in the UK, there will also be a hybrid version. The Active Hybrid 3 will be an official sponsor car at the 2012 London Olympics, able to travel for up to 2.5 miles on electric power alone and will average around 44mpg, despite having more than 300bhp.

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A four-wheel drive 3 Series also debuts in the UK, aimed to give drivers enhanced usability in tough weather and compete with the popularity of Audi's quattro A4.

The six-cylinder petrol engine from previous 328i models has been replaced with a four-cylinder turbocharged motor with 245bhp. Despite being much smaller, it's quicker than the outgoing model, hitting 62mph in 5.9 seconds and it's much more economical, managing 44mpg and emissions of 149g/km of CO2. The outgoing 330i took 6.2 seconds to 62mph, averaged 38.7mpg and emitted 175g/km of CO2.

With a boot increased in size by 20 litres to 480 and with a wider loading area, the 3 Series should be easier to live with too. Thanks to a 93mm increase in length, there's more room for people travelling in the back, with 15mm more rear knee room and 8mm more headroom.

BMW has also adopted a policy of testing all its new cars on our uniquely challenging British roads to ensure they handle to the desired level. In the past BMWs have received criticism for being too harsh over bumps, partly as a result of early run-flat tyre design.

The public will get its first chance to see the BMW 3 Series at the Detroit Motor Show from January 9, with first customers receiving cars in early February.