London Heathrow airport is examining the possibility of constructing its third runway on a ramp above the M25 motorway as opposed to tunnelling the road beneath the runway.

The airport says the gateway is looking at whether a ramp would be a "quicker and cheaper" way of delivering the runway but adds that its original proposal to tunnel the M25 is still on the table.

A public consultation process on the plans for a third runway will begin soon, adds the airport, and provide an opportunity for analysis of surface access options.

This will be followed two-and-a-half years later by Heathrow airport delivering a final proposal for the construction of the third runway to the Planning Inspectorate for scrutiny.

In an interview broadcast today, the transport secretary Chris Grayling told the BBC that an 8m ramp could be constructed consisting of "a very gentle hill up which the planes would take off".

In a Department for Transport study published yesterday, Highways England states that the surface-access proposals associated with the third runway represent "a series of complex interdependencies that each represents significant risk to the timeline" for the scheme.

The government agency adds that while the proposal for a tunnel to accommodate the M25 within the Heathrow proposals "is achievable within the construction timescales", A4/M25 interface work "represents a risk to the delivery of a new or extended runway".

Heathrow expects to begin construction of its third runway by 2021 and complete the work by 2025.

Source: Cirium Dashboard