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On the right road: Cycling for short journeys can really help the environment

There is no doubt that the bicycle has become the emblem of "going green".

The human-powered two-wheeler is to sustainable transport what the polar bear is to global warming - the easy-to-grasp symbol for more complex arguments.

You just have to think of David Cameron to see how mainstream cycling has now become a lifestyle choice - but not all cyclists have a car following them to carry their shoes, of course.

But how green is cycling and could actually using the bike gathering cobwebs in your garden shed actually have a positive impact on the environment?

There are several ways in which transport has an environmental impact: Manufacture, fuel used, maintenance, emissions and road building.

And in all these areas a bicycle scores above all the alternatives, bar walking.

A bicycle's manufacture, maintenance and disposal will necessarily have an environmental impact, but a bike only requires an estimated two per cent of a car's resources in manufacture.

Its size reduces the effects of transportation from the factory - more squeeze into the same space. The same applies to its disposal. Plus, it needs very little in the way of resources for maintenance.

Carbon neutral option

But the killer facts relate to fuel consumption and emissions. Essentially, a bike journey is always pretty much carbon neutral (meaning it contributes no CO2 to the atmosphere), plus non-polluting - no ultrafine toxic particles, no noise and no smell.

In contrast, 42.8 per cent of UK transport carbon emissions come from private motor transport (Defra, 2006).

Government figures show the average fuel consumption of UK cars now is about 1,280 litres of petrol (280 gallons) per year, and that generates about 2,940kg (2.95 tonnes) of carbon dioxide.

Throw in oil, antifreeze, car batteries and bulkier tyres and finding a more environmentally friendly option becomes a no-brainer. However, for longer journeys, the bicycle may be a less viable alternative - but it could make a real environmental difference in everyday life. Fifty eight per cent of car trips were under five miles and 25 per cent under two miles in 2004, according to Department for Transport (DfT) figures.

Meanwhile, only two per cent of short trips are made by bike (DfT) - but these are precisely the ones that could (or even should) be mainly made by bike. The WorldWatch Institute found that a four-mile round trip taken by bicycle rather than car keeps 15lbs of pollutants out of the atmosphere!

Money well spent

While the exact environmental impact of road building may be hard to measure, what is clear is that money spent on helping cyclists, such as building new cycle lanes and improved signing, is money well spent.

Sustainable transport charity Sustrans found that the cost-benefit ratio of improvements for cycling (and walking) schemes is equivalent to £20 for every £1 spent. The most obvious benefit (excluding the environment) being a reduced health care spend. Whereas a typical scheme for motorised transport would give a return of £2 per £1 spent - and motorways even less.

But you might think "why should I put in the effort to go green when the real impact can only come when governments change their practices?" While each individual change does only make a relatively small difference, as Sustrans argues, it DOES make a difference and it is relatively easy to make the change.

States and their institutions move slowly at best, whereas you could choose to start cycling to work tomorrow. Then not only are you benefiting the environment (and your conscience) but also your health.