How Heathrow’s third runway would pass over a widened M25
How Heathrow’s third runway would pass over a widened M25HEATHROW AIRPORT

Heathrow’s new runway over the M25 may lead to more accidents because of drivers being distracted by aircraft landing, according to roads officials.

An assessment of the airport’s plan for a third runway warns that the sight of huge passenger planes landing could cause motorists to take their eyes off the road.

Highways England has told Heathrow to introduce measures to “reduce driver distraction” on the affected section of the M25, Britain’s busiest stretch of motorway.

This could include lengthening the tunnel under the runway or simplifying the road layout to cut down on the number of decisions that drivers have to make. Heathrow was also told to consider the “landing zone of aircraft”, suggesting they should avoid arrivals directly over the road itself.

The comments are made in a series of reports produced by the government-funded company into Heathrow’s plan, which were obtained by The Times under freedom of information laws.

The airport wants to build a new two-mile runway directly over the M25, which widens to six lanes in each direction past the airport, carrying 220,000 vehicles a day. It is proposing to shift the motorway 150 metres to the west and lower it by 7 metres in a tunnel while also raising the runway slightly. Construction could begin as early as 2021.

The full details will be published for public consultation in June.

Highways England said the project was “deliverable” but that there were “concerns about several aspects of the design”.

The assessments warn that:

• The construction programme — which is likely to take more than five years — risks having an “adverse effect on traffic”, with the airport told that it will be banned from closing any lanes of the M25 between 5am and 10pm to avoid huge traffic jams in the area;

• There is a high risk of “fatigue damage” to the tunnel caused by aircraft as big as the A380 and Boeing 747, meaning that it could have a reduced lifespan;

• The runway must be “raised sufficiently above ground level” to avoid having to put the M25 in a steep tunnel beneath, with any gradient of more than 3 per cent causing lorries to move slowly, leading to congestion.

Highways England raises particular concerns about the risk of drivers being distracted by the sight and noise of passenger planes landing in their direct vision as they enter the tunnel.

Runways and taxiways have been built over roads elsewhere in the world, such as Atlanta and Fort Lauderdale in the US and Paris’s Charles de Gaulle. However, the sheer amount of traffic on the M25 and the number of planes expected to use Heathrow’s proposed northwest runway poses a particular challenge.

In a document delivered to Heathrow last March, Highways England said: “Consideration must be given to measures to reduce driver distraction as a result of the runway crossing the M25 and associated aircraft movements both on taxiways and take-off and landings. Measures which reduce decision making for motorists in this location should be considered.”

Jeremy Bloom, Highways England network planning director, said that Heathrow’s plan was “deliverable given appropriate mitigation”.

“By identifying and resolving potential issues at this early stage in design, we can make sure the final proposals will keep journeys on the M25 safe and reliable, both now and in the future,” he said.

A Heathrow spokeswoman said: “The options we’ve proposed for crossing the motorway are tried-and-tested at other airports around the world. Highways England have reviewed our early design and confirmed that our plans are robust and deliverable.”