Plans to introduce a third runway to Heathrow could see the busy M25 motorway moved into a tunnel. The consultation document includes proposals for a 3,200 metre runway, the end of which would pass over the top of the motorway.
MPs are expected to vote on the plans later this year. The construction would see the road shifted 150 metres west and lowered by seven metres to make room for the raised runway. The runway itself would also be cut by 300 metres from the originally proposed 3,500m.