How do you build a runway over a motorway?

How do you build a runway over a motorway?

Heathrow's third runway could involve planes taking off from a "ramp" over a motorway. How would this work, asks Harry Low.

There's an obstacle in the way of the proposed runway - the M25. An initial idea of constructing a road tunnel beneath the runway has been put aside. Building a "ramp" instead would be "a cheaper and quicker way of doing it", said Transport Secretary Chris Grayling.

Heathrow is situated near the the M25's busiest section, between junctions 14 and 15. Nearly 100 million vehicles flow through this stretch each year, according to Department for Transport figures.

Some on Twitter have joked that this ramp might resemble the front of some aircraft carriers that have a steep incline, known as a ski jump. "I can assure you it's nothing like that," says Chris Chalk, who's on the transport expert panel for the Institution of Civil Engineers.

"In fact, you wouldn't actually be able to see it with your eye. If you were on an aircraft you wouldn't know about it."


The gradient would be less than 1%, as required by the European Aviation Safety Agency. What impact would this have on a plane? "It doesn't affect the performance of an aircraft or provide any problems whatsoever," says Chalk.

"When an aircraft comes in to land, it's coming in at a gradient of about 5% so less than 1% is a very small difference. In fact, it's quite normal to have a runway with some gradient on."

Other UK airports that would have a greater gradient than that proposed at Heathrow include Bristol, Manchester and Birmingham.

How do you build a runway over a motorway?

Runway bridges have been built over busy roads including at Charles de Gaulle in Paris and Fort Lauderdale in the US state of Florida. Planes taxi along a bridge over a motorway at Leipzig-Halle airport in Germany and at Amsterdam's Schiphol Airport.

Designers are required to allow a large amount of space either side of the runway in case there is an incident on the airfield. Strategically placed slats and the right lighting will be factors in preventing drivers from losing concentration due to planes overhead, explains Chalk, who works for the civil engineering firm Mott MacDonald.

"You tend to have a number of visual buffers because you don't want to distract the drivers. At that distance you won't actually be seeing the aircraft that easily. It hasn't created any issues elsewhere at other busy airports."

So those thinking the boredom of being stuck in traffic on Britain's busiest motorway might be relieved by the sight of a large aeroplane crossing the road will be disappointed.



Add Comment

all comments

  Other news

more
‘Nobody will like’ govt shutdown over border wall, Senate Dems leader says

‘Nobody will like’ govt shutdown over border wall, Senate Dems leader says..

23-Aug, 15:40

Shutting down the US government over funding for the border wall will be...

Trump says he'll probably kill US trade pact with Canada & Mexico

Trump says he'll probably kill US trade pact with Canada & Mexico..

23-Aug, 07:30

US President Donald Trump has warned he might scrap the North American...

French firm offered spyware to 'find out if your son is gay'

French firm offered spyware to 'find out if your son is gay'..

23-Aug, 12:30

A French company offering "invisible PC spy software" has been criticised...

Andy Burnham: North 'needs transport investment now'

Andy Burnham: North 'needs transport investment now'..

23-Aug, 10:20

The north of England "needs transport investment now", the Mayor of...

Malaysia says airport safe, autopsy shows nerve agent effect

Malaysia says airport safe, autopsy shows nerve agent effect..

25-Feb, 19:34

Malaysia's health minister said Sunday autopsy results suggested a nerve...

Cyclist killed in Colorado canyon was student from Brazil

Cyclist killed in Colorado canyon was student from Brazil..

06-May, 14:25

A coroner has identified a bicyclist who died after being hit by a pickup...

Battle Bay Hack & Cheats: Download Battle Bay Mod APK

Battle Bay Hack & Cheats: Download Battle Bay Mod APK..

07-May, 10:08

Battle Bay Hack & Cheats Rovio Entertainment is one of the most popular...

China shuts only undersea coal mine amid production rebound

China shuts only undersea coal mine amid production rebound..

24-May, 00:21

China is shutting down its only undersea coal mine as the government...