Plans have been submitted by a group of three companies to the Department for Transport to build a new high-speed rail line HS4Air, which would connect HS1 and HS2 in the South East with the western region of the country, in addition to providing faster journey times to Heathrow and Gatwick


(Credit Weston Williams + Partners / Engineering Expedition)

The first leg of HS2 won’t be built for at least another eight years, while HS3 remains a pipe dream for now – but already plans have been drawn up for a fourth high-speed rail line known as HS4Air.

A £10bn vision has been unveiled by a group of businesses for a 140km railway that will connect HS1 – the Channel Tunnel rail link – in the country’s south-east region with HS2 north west of London.

It would link up the existing and new high-speed rail infrastructure with Britain’s busiest airports by including stops at Heathrow and Gatwick, as well as a spur connection to the Great Western main line.

The concept has been developed by London-based Expedition Engineering with architect Weston Williamson + Partners (WW+P) and planning consultancy Turley.

The HS4Air plans – which were drawn up in response to an invitation by Transport Secretary Chris Grayling for third parties to come forward with ideas for a new southern rail link to Heathrow – will now be submitted to the Department for Transport (DfT) to consider.

Expedition Engineering director Alistair Lenczner said: “As a joined-up, strategically important piece of infrastructure, HS4Air offers new connectivity that will provide an economic boost for the entire country.

“The multi-benefit nature of the project means that it will offer a better return on infrastructure investment than is often the case for infrastructure projects that have only a single primary objective.

“HS4Air will overcome the barrier that historic London represents in terms of rail connectivity between the UK regions and Europe.

“By allowing London to be bypassed at high speed, economic activity between the UK regions and Europe can expect to grow.

“The very positive response the HS4Air project has received from various parties suggests that the proposal can expect widespread public support as it moves forward.”


What is HS4Air?

The new HS4Air railway will include stations at Ashford and Tonbridge, both in Kent, with the aim of improving the regional economies between south east England and northern England.

A 15-minute shuttle service between Heathrow and Gatwick will also help the two airports share capacity by establishing a quick connection between the two.

HS4Air will have the following estimated journey times:

  • Ashford-Gatwick: 25mins (currently 1hr 50mins)
  • Manchester-Heathrow: 1hr 10mins (currently 3hrs 20mins)
  • Heathrow-Gatwick: 15mins (new route)
  • Cardiff-Heathrow: 1hr 40mins (currently 2hrs 50mins)
  • Birmingham-Paris: 3hrs (currently 3hrs 50mins by plane)
The proposed HS4Air route (Credit: Expedition Engineering)

By connecting Britain’s two high-speed lines to the west of the capital through the link with the Great Western main line, the developers argue HS4Air will remove a detrimental barrier between western England and mainland Europe.

It is also expected to reduce the pressure on London’s highly congested rail network by accounting for some of the passengers and freight requirements that would normally pass through the capital on their way to the country’s West or North.

Plans for minimising the environmental impact of the project include building the rail line to follow alongside the M25 west of London and tunnelling under critical rural areas, along with re-using and improving the existing line between Ashford and Tonbridge.

WW+P associate partner Nick McGough said: “HS4Air takes the problem of linking HS1 with HS2 and turns it into an opportunity in by-passing London entirely while better connecting the UK’s two largest airports and the country generally through high speed rail.

“It is exciting that the DfT’s Rail market-led proposal initiative opens the door for this sort of innovative proposal.

“HS4Air can help unlock opportunities for much-needed housing in the South East through joined-up and sustainable infrastructure development.”

Director of economics at Turley, Amy Gilham, added: The HS4Air proposal ties in with many of the UK Government’s economic growth objectives.

“By reducing journey times by rail the line will help to deliver the Government’s main ambition of its modern Industrial Strategy – to reduce the productivity gap across the country.

“It will also help to deliver much needed housing and employment growth in areas of recognised pressure, particularly the South East, by opening up sites and creating opportunities for sustainable development.”


HS4Air is the ultimate dream – but what is HS2?

The UK’s second high-speed rail line is estimated to cost £56bn and will transport passengers at speeds of up to 250mph.

Two new fleets of trains will run the service – one solely for the HS2 network and another smaller fleet, which will also be compatible with existing train stations in Carlisle, Edinburgh, Glasgow, Liverpool, Newcastle, Preston, Sheffield and York.


HS2 route map

While the first train journeys on the HS2 route are scheduled to begin in 2026, phase 2b – connecting Crewe to Manchester and the West Midlands to Leeds – will not be completed until 2033.

Obstacles to the project range from a potential lack of demand and the environmental damage involved with building another national rail line to the potential exacerbating of the North-South divide if HS2 encourages more people based in the regions to commute to the capital for work rather than take jobs in their home cities.

Yet the potential draw of a much shorter commute, as well as increased accessibility for the UK’s biggest city, remains.

It will serve more than 25 stations, connect eight of Britain’s ten largest cities and serve 30 million people – almost half the population.

View the updated journey times here.

What are HS1 and HS3?

The UK’s first high-speed rail line is a 108km route between London and the end of the Channel Tunnel.

It transports passengers between the UK and Europe, as well as between Kent in the East of England and London.

It cost £5.8bn to build and opened officially on 14 November 2007.

A HS1 train (Credit: Flickr, Les Chatfield)

Also known as Northern Powerhouse Rail (NPR), HS3 is Britain’s third proposed high-speed rail line, aiming to improve connectivity in the north of England, connecting Liverpool, Manchester, Manchester airport, Leeds, Huddersfield, Sheffield, Newcastle, Hull, and other key economic centres.

A point-by-point strategic business case HS3 is due to be completed by the end of 2018, with the project reportedly estimated to cost about £7bn.