Costly plans to replace Hammersmith flyover with a tunnel mean motorists could pay tolls

Motorists could be forced to pay tolls on one of London's busiest main roads under costly plans to replace a flyover with a tunnel.

Credit: Google Street View

Transport for London is to carry out a feasibility study into replacing the A4 Hammersmith flyover with a 'flyunder'.

Boris Johnson announced a detailed investigation into the cost of the scheme during his official visit to the US.

Boston, USA Credit: ITV News

The mayor saw a similar project in Boston where a six-lane elevated highway was buried in a series of tunnels.

But the Central Artery Tunnel Project, known as the Big Dig, was a financial scandal running years behind schedule.

Boris Johnson in Boston Credit: ITV News

The cost of the work spiralled out of control from $2.8bn to $22bn, making it America's most expensive new road.

Critics called it America's 'Greatest Highway Robbery.'

Boris Johnson in Boston Credit: ITV News

Rebuilding some of our complex and aging road network underneath our city would not only provide additional capacity for traffic, but it would also unlock surface space and reduce the impact of noise and pollution.

I am inspired by what the ambitious people of Boston have achieved here at the Big Dig, both in terms of reducing congestion and how they have dramatically improved the quality of life on the surface.

In London we face similar challenges on our roads, but this could also be a fantastic opportunity to better shape our city and support economic growth.

– Boris Johnson, Mayor of London

Boris Johnson also announced studies into the cost of creating new tunnels at four other sites - the A13 at Barking Riverside, the A3 in Tolworth, the A316 at Chalkers Corner and the A406 at New Southgate.