The chief executive of London’s Heathrow Airport has said the controversial new runway backed yesterday by the UK government could be built as a bridge over the busy M25 motorway to prevent horrendous traffic disruption.
The plan had been to divert the busiest stretch of motorway in Britain and send it underground for 650m so that it went underneath the third runway, which would have been built at ground level.
But concerns have been raised by Highways England, a roads authority, that the new runway would cause gridlock on roads around the airport, already prone to jams.
In response, the airport’s chief executive John Holland Kaye told newspaper The Times that the tunnel plan might now be ditched in favour of building the runway on a man-made hill using spoil from the construction project.
This hill could slope upwards to a height of eight metres above the ground where it crosses the M25, making the runway a bridge over troubled traffic.
The approach has been used elsewhere, including at Florida’s Fort Lauderdale-Hollywood International Airport (pictured), where engineer Atkins extended the runway to 2.4km out over roads and a railway.
There the new runway rose to an end height of just under 16m (52 feet) when it was finished in September 2014.
"An alternative is for a bridge over the existing M25; that’s something that’s been done in lots of other places and lots of other airports actually," John Holland Kaye told The Times.
He said that the plan would be developed during consultation, adding: "What you do is you have the runway on a gradual slope; and I think the highest point is eight metres above the current grade."
The M25 widens to six lanes in each direction past Heathrow, and has been called the busiest stretch of motorway in Britain.
The plan agreed by government yesterday sees it diverted for 2.5 miles and then tunnelled for 650m under the third runway.
But The Times found a letter from Ginny Clarke, director of strategy and planning at Highways England, saying that the tunnel would cause "disproportionate disruption to traffic flows" when built.
Her letter also said that the runway would "involve significant disruption during construction". The Highways England report said that the plans would "place significant pressure on . . . contractors’ resources", with "growing national impacts" on other road-building schemes.
Image: The new runway at Florida’s Fort Lauderdale-Hollywood International Airport was extended 2.4km out over roads and a railway in 2014 (Atkins)