The plans, imagined as part of a challenge from think tank New London Architecture for new ideas to improve life for Londoners, would make commuters happier and healthier, the designers claim.

The Circle Line is one of London’s most congested, carrying 114 million people each year along 17 miles of track. The line is perceived as being the slowest and least reliable of the city’s network, but the ambitious proposals claim that the conversion would at least match current commuting times.

This year it celebrates its 110th anniversary since becoming electrified - but architects from London’s NBBJ firm say converting it to a walking superhighway would mean it could take more people - and those travelling on it could complete their journey faster.

The travelator would consist of three lines; a feeder line moving at 3mph onto a yellow “slow lane” going at the same speed through stations but accelerating to 6mph and then 9 mph in lit tunnels.

There would also be a “middle lane”, coloured orange, with a top speed of 12mph, and a 15mph red “fast lane”.

NBBJ researchers calculate the travelator would allow up to 55,000 people to use the Circle line at any one time.

NBBJ said: “The Circle Line carries 114 million people each year.”

“Currently able to accommodate eight trains at any one time and reach a top speed of 20 miles per hour, the line is one of the most congested in London, often subject to delays and frequently unpleasant for overheated commuters.”

The firm has previously developed proposals for an ambitious ‘shadowless skyscraper’.