A CABLE car is among the green ideas being put forward by London Assembly Green Party members as an alternative to the proposed six-lane Thames Gateway Bridge.

Other alternatives in a new report commissioned by the Greens and funded by Transport for London (TfL) include a ferry, a light rail transit and a public-transport-only bridge with provision for cyclists and pedestrians.

But it is the cable car proposal which has caught people's imagination and is supported by the Campaign for Better Transport (CBT) among others.

A CBT spokesman said: "The proposal for a cable car will surprise some people, but fresh thinking is needed and this is an imaginative option.

"Above all, TfL needs to come up with an appraisal of options which produces a genuinely sustainable decision, not the same old approach of more roads, more traffic and more pollution."

The report says while many Londoners will be familiar with the use of cable cars for transport in mountainous regions, they have been increasingly used in recent years in cities such as Barcelona and Istanbul.

It says one of the best examples of a cable car used as a river crossing is in New York, where the Roosevelt Island Tramway spans the East River and is 3,100ft long.

Each cabin has a capacity of 125 people and it makes 115 trips a day, taking four-and-a-half minutes to make the crossing.

It is accessible for wheelchairs and carries bicycles.

In Cologne, Germany, a cable car has crossed the River Rhine since 1957 and Medellin, Columbia, uses two cable car lines as part of its metro system.

One has a capacity of 3,000 people an hour.

The Greens approached a commercial company and one of the world leaders in cable car planning and production which looked at the requirements of crossing the Thames and it has said the idea is technically feasible.

With existing navigation and aviation restraints from London City Airport taken into consideration, the company, Doppermayr, says a cable car system could carry a maximum of 4,000 people an hour in each direction.

The average speed would be around 15 mph and crossing time would be around two minutes.

With cable cars arriving every 22 seconds, there would be hardly any waiting time, and they are as close to zero emissions as any powered method of transport can be.