A plan for a new 140km long high-speed rail line dubbed an “M25 for high speed trains” has been proposed by consultant engineers Expedition.
The new line “HS4Air” is being proposed to start at the HS1 station in Ashford in Kent, then run south of London to Denham near the Colne Valley, where it would link with the High Speed 2 (HS2) line.
The estimated cost of the line is £10bn, based on an estimated pro-rata equivalent cost per mile of HS2 Phase 1.
HS1 terminates at St Pancras in London and HS2 will terminate at Euston Station, a 20 minute walk away, however construction of a direct rail line between the two is not in the HS4Air plan. Expedition director Alistair Lenczner said a link between the two was originally proposed for HS2, but was taken out of the scope due to the additional cost of the scheme.
Lenczner said the lack of a through link was a big inconvenience for passengers who would have to leave Euston station, walk and then check in and wait for HS1. The new line would therefore provide a direct link between the two without having to change in Central London.
He said research showed that passengers were far more likely to pick a journey which involved the fewest and least complicated or onerous changes.
“Not only is this new link better in terms of convenience because you can sit in a single seat from Birmingham to Paris, but in terms of timing,” he said. “It would potentially save up to two hours, by not having to change in central London.”
The proposed route for the line also creates a connection to Heathrow and Gatwick Airports and the Great Western Main Line railway (GWML) to the north of Heathrow.
Lenczner said the rest of the country would also benefit as passengers from the north or south would no longer have to go into central London to travel to Heathrow and Gatwick Airports. This will relieve pressure on the road network, save time and be more environmentally friendly, he said.
In addition to this, he said a shuttle service could be run on the line between the two airports allowing them to work together rather be in direct competition.
“At the moment it takes an age to get between the airports,” he said. “If the airports had a direct connection, they could design the routes to take this into account and open up capacity. There could even be an airside link depending on how it is designed.”
Under the proposals around 40% of the 140km line will run on upgraded existing lines from Ashford to Tunbridge, 20% would run in tunnel predominantly under the Surrey hills and another section would run alongside the M25 near Heathrow.
Lenczner described current infrastructure as working in “silos” and said the new line would “enhance the benefits of using existing infrastructure, save money and make the assets multi use”.
“The proposed HS4Air project is an example of integrated strategic planning that spans across multiple infrastructure sectors that are too often planned within separate silos, he said. “Such integrated planning allows projects to achieve better results in terms of their land-use efficiency and investment value.”
The new link mimics lines in other countries, Lenczner said.
“If you go to from Lille to Marseille you can do that on a direct train service which passes around Paris and goes through Charles de Gaulle Airport,” he said. “We’re learning lessons from good practice which has been done in other countries.”
Lenczner introduced the HS4Air proposal as part of his talk at the event called ‘How London’s pioneers built our city, London’ at the Institution of Civil Engineers in London last night.