London Mayor Boris Johnson has unveiled plans for a floating motorway to be constructed on the River Thames, intended to ease congestion in the city ahead of the London 2012 Olympic games this summer.

Due for completion in July, the design by London studio Dowling Jones and Stone will include an access junction at Tower Bridge and stretch from Wandsworth to Limehouse along the water.

The announcement comes exactly one year after Dowling Jones and Stone unveiled their design for a 12 metre-high bronze statue of Johnson overlooking the river - see their proposal here.

Here are some more details from the designers:

London Mayor Boris Johnson has unveiled audacious emergency plans to avoid total gridlock in London during this Summers Olympic Games. Boris left Londoners amazed as he today unveiled a floating Olympic motorway that will stretch from Wandsworth 7 miles to Limehouse along the famous Thames. The scheme was hastily developed after traffic plans for the Olympic Games including the infamous Olympic Lanes were widely criticised. The floating lanes, controversially ear marked for use only by official Olympic cars will feature a major access junction at the world famous Tower bridge. The 118 year old structure will be adapted to allow access to the river road. The huge temporary structure costing £12 million will be hastily constructed and floated into place and assembled in time for the start of the games in July.

Gregg Stone of designers Dowling Jones & Stone, the London based consultants said ”the games is an extraordinary event and London presents unique transport challenges, taking to the river was the only way to keep things flowing".

Boris will come under pressure from transport groups as he plans to limit access to Olympic fat cats only and the huge price tag connected with the project but he is keen to appease worried London voters in an Election year.

Dowling Jones and Stone are based in London and create visualisations of architectural concepts.