Urban Myth - Thames Valley

[libby1980]

There is a rumour that part of the M4 near Heathrow is intentionally straight with no bridges so that it could be used as an 'extra' runway for Heathrow if it was needed in an emergency. Has anyone else heard this or know if it's true?

[iaintsm]

In the 1950s and 1960s the government decided that every motorway in the UK had to have at least one mile straight and no bridges as to allow military aircraft to land and take off from during an attack or invasion during the Cold War.

[spudqueen]

It is true that in the States one mile in every (is it five or ten) is straight to act as an emergency runway.

[kempie]

Sorry spudqueen but it is definitely an urban myth that in the US the Eisenhower Interstate Highway System requires that one mile in every five must be straight for as airstrips in times of war or other emergencies.

http://www.tfhrc.gov/pubrds/mayjun00/onemilein five.htm

[gary baldy]

There is a stretch of the M62 near warrington that also carried the same myth. This may have arisen because the particular stretch of motorway was built directly above the former runway of Burtonwood air base. Up until very recently this very straight bit of motorway had no bridges and a seemingly temporary central reservation that looked like it could be removed very easily. This only added to the myth but was never confirmed.

Saying all that though BAe Jaguar aircraft used the M55 near Blackpool before it was open to the public as a test runway should such an occasion arise.
There is an amazing picture here:
http://www.iht.org/motorway/m55pnb.htm