The first ever study of the impacts of one-way car-sharing services in North America shows that over the past three years there are already noticeable benefits in terms of pollution levels and traffic volumes.

The study, conducted by the University of California, Berkeley Transportation Sustainability Research Center (TSRC), focused solely on one service -- car2go -- and on data from its 95,000 members across Calgary, San Diego, Seattle, Vancouver, and Washington DC.

And the headline figures are impressive. Each car2go car in the company's fleet has removed as many as 11 other vehicles from city streets, meaning that across those five cities there are currently 28,000 fewer cars on the road causing congestion and taking up parking spaces.

"Our exhaustive, three-year research effort into one-way car-sharing reveals that car2go vehicles result in fewer privately-owned vehicles on the road, fewer vehicle miles traveled and a reduction in greenhouse gas emissions," said Susan Shaheen, Co-Director of TSRC.

However, there are other positive side effects from joining a "free-floating one-way" car-sharing service. For example, between two and five per cent of car2go members have sold their cars because of the service, and the average age of those cars being disposed of was 14.4 years, meaning that they are some of the more polluting and least economical vehicles on the road.

A further seven to 10 per cent of members said that due to signing up to the service, they didn't need to buy a car.

Unlike conventional renting or leasing services, one-way serices mean that the member need only drive the car to his or her final destination and leave the car, rather than drive it back again after the sharing period is over. Eliminating these return journeys adds up quickly with car2go members cutting miles traveled per year on average by 11 per cent. This in turn translates into an average 10 per cent reduction in greenhouse gas emissions.

"TSRC's findings make it clear that one-way car-sharing has a significant and beneficial impact in reducing private vehicle miles traveled and emissions in cities, ultimately helping more people get where they want to go more efficiently while helping to reduce traffic and parking congestion," said Paul DeLong, president and CEO of car2go North America.