Construction Enquirer
Aaron Morby
01 October 2025
Heathrow has mapped out how it will tackle one of the UK’s most complex motorway upgrades while keeping traffic flowing on the country’s busiest stretch of road.
The airport’s third runway scheme will need a brand-new section of the M25 to be built, complete with a tunnel and new bridges, at Junction 14 near Heathrow.
Rather than rebuilding in place, Heathrow will construct the new motorway 130 metres to the west of the existing road to avoid traffic chaos.
This “offline” approach means most of the heavy works will take place away from daily traffic.
Once complete, traffic will be switched from the old alignment onto the new during a series of planned overnight closures.
The re-engineered stretch will be wider and safer, with new link roads to untangle weaving movements between the M25 and M4.
