If New Zealanders increased their cycling to the modest levels of the 1980s, they would burn off annually the amount of energy contained in 40 million cans of Coke.

And this is just commuter and local cycling at a relaxed pace - not a Hayden Roulston-style medal-winning sprint in lycra. Commuter cycling has collapsed since the 1980s and less than 2 per cent of people bike to work.

The calculations come from a paper prepared by Auckland University researchers for the New Zealand Transport Agency.

The agency is guided by the New Zealand Transport Strategy, whose aim is that by 2040, 30 per cent of urban trips are made by bike, on foot or other "active modes" of travel.

Research fellow Dr Graeme Lindsay and colleagues studied the likely effects of shifting 5 per cent of urban light-vehicle trips of 7km or less to cycling and found savings in fuel consumption, greenhouse gas emissions.

More than five lives would be saved through reduced air pollution from vehicles. This would be largely negated by an additional five cyclist deaths from crashes. However, they found that as the proportion of vehicle trips shifted on to bikes increased, the "safety-in-numbers" effect progressively reduced the cycling death rate, even though the total number of cyclist deaths rose.

But the biggest health effect would be through the reduced rate of conditions like heart attack and cancer among commuter cyclists and the kilos of body fat shed.

All that pedalling would burn up the equivalent amount of energy of 40 million cans of Coke - a potential fat loss of 675,000kg, and 116 deaths would be saved by improved health.

Dr Lindsay said last night that the health of New Zealand would improve significantly if the country returned to the regular commuter cycling levels of the 1980s.

The paper relies on World Health Organisation estimates based on large studies which indicate mortality from all causes was reduced by 30 per cent among regular adult commuter cyclists.

"The studies, from Denmark and China, found consistently fewer deaths than expected from cardiovascular diseases and cancers, and reported this finding could not be explained by recreational activities or other lifestyle factors," the paper says.

"In New Zealand, bicycles are now seldom used for commuting. Overall, bicycling makes up about 1 per cent of all trips in this country compared to 3.6 per cent in 1989/90. In contrast, some northern European countries have figures of 20 to 30 per cent."

Shifting 5 per cent of urban light-vehicle trips of 7km or less to cycling is calculated annually to reduce:
* Fuel consumption by 22 million litres.
* Transport-related carbon dioxide emissions by 0.35 per cent.
* Air pollution deaths by 5.6.
* Premature deaths from ill health by 116.
* Body fat by 675,000kg, potentially.

The down side:
* Cyclist crash deaths up by 5.