Heathrow consultation: their suggestions of how to deal with M25, tunnel, bridge, altered junctions etc

As part of its consultation on its proposed 3rd runway, Heathrow has a section on what it hopes is done with the M25, so the runway can go over it.  This is a very expensive and complicate operation, and Heathrow is keen to cut the cost. The proposed runway will cross the M25 between Junctions 14 and 15 (J14 and J15) and will affect the operation of J14 and J14a, but not J15.  Other than moving the motorway a long way west, the options are tunnelling or bridging. Heathrow says: “Our current thinking is to re-position the M25 carriageway approximately 150 metres to the west, lower it by approximately 7 metres into a tunnel and raise the runway height by 3 to 5 metres so that it passes over the M25 between J14a and J15. The motorway will then re-join its current route. …We believe this approach is the most deliverable as it would allow construction to proceed while the existing M25 motorway remains in operation. This minimises impacts to road users and has the least overall impacts on communities during construction and long-term operation.”  And they say the 3rd runway will mean more traffic will want to pass through junctions 14 and 14A, so they will need to be expanded. Illustrations show some different options.



Heathrow expansion: M25 to be moved and section put in tunnel to allow runway to stretch over busy motorway

The motorway could be moved 150 metres to the west and lowered into a tunnel to accommodate the runway

By Qasim Peracha (Get West London)
17 JAN 2018

Section of the Heathrow consultation papers, on the M25, at   https://www.heathrowconsultation.com/our-emerging-plans/roads-and-the-m25/

Heathrow Airport has put forward new options to move the M25 carriageway and tunnel a section in order to make way for the proposed third runway .

The “realignment” options are part of the consultation launched on Wednesday (January 17) by the airport to encourage people to have their say on the plans for expansion.

If constructed, the North West Runway would extend several hundred metres past the current M25, between Junction 14 and 15, and the airport has come up with proposals to relocate the carriageway in order to extend the runway.

Heathrow plans to move the carriageway 150 metres west of its current site and lower it seven metres into a tunnel.

Heathrow also wants to raise the runway height by three to five metres, allowing planes to land and take off above the motorway between junctions 14a and 15.

Under the runway, segregated carriageways may separate traffic using the M25 as a “turning movement” between Junctions 15 for the M4 and 14 for Heathrow, from “mainline traffic”.

A CGI of the tunnel section of the M25 (Image: Heathrow Airport/Grimshaw Architects)

The “collector distributor” roads would prevent risky lane changes and help the flow of local traffic not using the airport.

Heathrow would not be the first airport to build a runway over a motorway, with a similar runways at Paris’ Charles De Gaulle Airport and Atlanta’s Hartsfield–Jackson Airport.

Heathrow expansion: M25, terminals and flight paths on the table as airport launches largest ever public infrastructure consultation

The airport says in its consultation documents that it has “discontinued” plans to bridge over the current M25 or tunnel under the runway, due to its complexity and impact on road users.

The third runway will extend over the M25 but the length of it and options for the relocation of the M25 are up for consultation.

The plan to relocate the M25 would allow one of the busiest stretches of the orbital motorway to remain open while the new stretch is built alongside.

As well as moving the runway, the airport has come up with a number of options to change the junctions, with Junction 14 looking set for a major overhaul.

Junction 14a may be axed by the airport, if new terminal facilities are located west of the current Terminal 5 site.

Two possible proposals for the new layout of the M25 between Junctions 14 and 15, below the third runway (Image: Heathrow Airport)

Instead a series of flyovers may be built from Junction 14 to the airport in order to deal with the knock-on effects of the loss of the Northern and Western Perimeter Roads if the runway is built.

The 10-week consultation launched on Wednesday (January 17) and closes on March 28. Other aspects of the consultation include where terminal facilities should be moved and how airspace should be remapped.

To find out more details about the consultation events, detailed proposals and to respond to the consultation visit the website . https://www.heathrowconsultation.com/




This is what the Heathrow consultation website says about the M25:

M25 alignment and junctions

The construction of a new north west runway will extend the airport to the west. The proposed runway will cross the M25 between Junctions 14 and 15 (J14 and J15) and will affect the operation of J14 and J14a.

The M25 is one of the busiest roads in the UK and we will ensure that our proposals do not result in disruption. We are working with Highways England, who are responsible for the operation, maintenance and improvement of the motorways and trunk roads in England, to ensure the project meets their design and safety standards. We demonstrated our track record in changes to the M25 when we built J14a as part of the Terminal 5 project.

Tunneling the M25

We have looked at options to bridge the runway over the M25, to tunnel the M25 under the runway (our previous design concept to the Airports Commission), or divert the M25 around the west end of the runway. The new level of the M25 will be determined by design standards so that it works with the existing J15 which we are not planning to change.

Our current thinking is to re-position the M25 carriageway approximately 150 metres to the west, lower it by approximately 7 metres into a tunnel and raise the runway height by 3 to 5 metres so that it passes over the M25 between J14a and J15. The motorway will then re-join its current route.

Crossing a motorway with a runway or taxiway has been done successfully at other airports around the world such as Paris (Charles de Gaulle) and Atlanta.

J15 will not be affected but some minor works may need to take place to tie the main carriageway and link roads into the junction. We believe this approach is the most deliverable as it would allow construction to proceed while the existing M25 motorway remains in operation. This minimises impacts to road users and has the least overall impacts on communities during construction and long-term operation.

We are also considering whether there would be benefits in introducing collector-distributor roads alongside the M25 that improve journey times for both airport and non-airport traffic. Such roads are however complex to build, require more land and are more costly.

M25 junctions

The expansion of the airport and realignment of the M25 will mean that we have to make some alterations to Junction 14 (J14) and Junction 14a (J14a).

An expansion of the airport to the north west, and a need to alter some local roads (see Local roads), is likely to mean more traffic will want to pass through these junctions and so we will need to improve their capacity. We are currently considering two ‘families’ of options for these junctions:

  • Family 1 – both J14 and J14a are retained: J14 will need to be redeveloped to accommodate the displaced traffic movements from surrounding areas and maintain good connections to nearby communities. J14a may need to be altered to fit with the westerly expansion of the airport. Both junctions may need altering to accommodate collector-distributor roads.
  • Family 2 – J14a is closed: J14a currently provides direct access to T5, but if T5 and the western apron is expanded (see section 2.2), the junction may have to be permanently closed. In those circumstances, J14 would need to be redeveloped to accommodate the displaced road traffic from J14a. More space and road adjustments may also be required for collector distributor roads.

Both options require the redevelopment of J14. Our preference is for options that provide short journey times for airport and non-airport road traffic, provide good connections to nearby communities whilst minimising property loss and construction effects on Stanwell Moor and Poyle.




See earlier:

IAG warns the “costs and complexity” of bridging M25 could be major problem for Heathrow runway plans

British Airways’ owner International Airlines Group (IAG) estimates bridging the M25, close to the M4 junction, would cost £2 billion-£3 billion. The Airports Commission suggested the cost could be higher, with £5 billion for local road upgrades, including the tunnel. The Commission said Heathrow should pay for these, as part of the cost of building its runway. The cost and complexity of somehow putting the runway over the busiest, widest section of motorway in the UK are considerable.  IAG, as by far the largest airline at Heathrow, does not want to be charged for this work, which would mean putting up the price of its air tickets.  IAG says there is no detailed risk and cost analysis of the airport’s plans on what to do with the M25, though a bridge is cheaper than a tunnel.  Willie Walsh said: “Airlines were never consulted on the runway length and they can operate perfectly well from a slightly shorter runway that doesn’t cross the M25.” He wants Heathrow to build a shorter runway of 3,200m rather than 3,500m that does not require going over the M25. But that would mean the motorway directly at the end of the runway, in the worse danger zone. IAG says: “We will not pay for a runway that threatens both costs and delays spiralling out of control and where critical elements of the project could be undeliverable.”




Heathrow now considering (not tunnel or bridge) but cheaper series of “viaducts” over M25

Heathrow has a huge problem in how to get a runway over the busiest, widest stretch of the M25.  The original plan was a full 14-lane tunnel about 2,000 feet long. Then there were plans for a sort of bridge over the road. Even those would be prohibitively expensive (Heathrow says it would only pay £1.1 billion on roads etc). Now there are plans, by Phil Wilbraham, who oversaw the construction of Heathrow’s terminals 2 and 5,  to build a cheaper system. It would be 3 parallel bridges across the M25, with narrow ones for taxiways at the side, and a wider one for the runway in the centre. The plan is for a 2 mile long runway, to take even the largest planes. The main airline at Heathrow, British Airways, suggested a runway about 1,000 feet shorter, that would not need to cross the motorway, but that might not be able to take A380s, and would mess up the flight patterns.  The earlier “bridge” concept would have meant the runway would be on a slight slope, to get over the motorway. The cost of moving the thousands of tonnes of earth would be immense, and it is thought Heathrow has had to reconsider. The airlines do not want to have to pay for the building costs of roads etc associated with a 3rd runway. The government does not want to force Heathrow to pay, as this would mean increasing the cost of flying – and reduce demand at Heathrow.




Heathrow boss rules out footing the £5 billion bill for road and rail works – wants taxpayer to pay

The Airports Commission left the matter of who would pay for the approximately £5 billion needed to tunnel a section of the M25, and other surface access improvements, vague. The assumption has been made that the taxpayer would have to fund this, though the Airports Commission suggested that Heathrow would be able to find the funding from its investors for this. Now the CEO of Heathrow has dismissed the suggestion that the airport foots the £5 billion bill for road and rail work if a 3rd runway is built.  Huge motorway engineering would be needed, to have the runway going over the motorway.  John Holland-Kaye has ruled out paying for the surface access work. Though the government funds road and rail improvements under normal circumstances, tunnelling the M25 and dealing with hugely increased road traffic using an airport 50% larger than at present are not normal circumstances. Especially in times of huge economic savings being necessary in public finances. The Commission’s final report said it considered the runway was commercially viable “without a requirement for direct government support. This remains the case even in a situation where the airport is required to fund 100% of the surface access costs.” This would be by Heathrow “raising both debt and equity finance. This finance is then serviced through subsequent revenues and refinancing by the airport operator.”    



Times reports that Heathrow plans to offer to cut costs and build runway scheme faster

The Times reports that it has learned how Heathrow is planning to cut up to £3 billion (out of about £17.6 billion) from its plans for a 3rd runway, in order to persuade Theresa May and the Cabinet that the runway could be delivered – and delivered a year earlier. Revised plans include potentially scrapping plans to tunnel the M25 under the 3rd runway, not building a transit system to carry passengers around the airport (using buses instead) and smaller terminal buildings. The aim is not only to get the runway working by 2024 but also -with reduced costs – keeping charges for passengers a bit lower. The Airports Commission estimated the cost per passenger would need to rise from £20 now to £29. Airlines like British Airways are not prepared to pay such high costs, and especially not before the runway opens.  BA’s Willie Walsh has described Heathrow’s runway plans as “gold-plated”. The Times expects that Heathrow will announce its new “cheaper, faster” plans by the end of September.  There is no mention of the “Heathrow Hub” option of extending the northern runway – a slightly cheaper scheme than the airport’s preferred new north west runway.  There is no clarity on quite what Heathrow plans for the M25, if they cannot afford to tunnel all 14 lanes (at least £ 5 billion).  Lord Deighton said it might be “diverted” or have “some form of bridge.”