HS4Air – “An M25 for high speed trains”

HS4Air (High Speed for Air) is a proposed strategic high-speed rail/air connection in south east England developed by Expedition director Alistair Lenczner.

The proposal is for a new high-speed railway connection that links the existing HS1 line with the planned HS2 line passing via both Gatwick (LGW) and Heathrow (LHR) airports to the south and west of London.

The proposal is seen as offering multiple benefits across several infrastructure sectors. These include:

  • Fast direct rail access to both LGW and LHR from major cities north and west of London including Birmingham, Manchester and Cardiff
  • Dramatically reduced journey times for rail journeys between south east England and the Midlands, North and West UK
  • Direct high-speed train services from Manchester and Birmingham to Europe via the channel tunnel
  • A 15-minute transfer time between LGW and LHR allowing them to share operations
  • Fast rail freight services by-passing London to allow dramatically faster logistics operations
  • Relief for London’s rail network leaving more capacity for Londoners.

HS4Air would minimize its introduction into the environment of South East England by doing the following:

  • Being twinned with the M25 to the west of London
  • Passing in tunnels under sensitive rural environments such as the North Downs
  • Re-using the existing railway between Ashford to Tonbridge upgraded for high speed running.

In addition to the benefits mentioned above, HS4Air is also seen as an opportunity to introduce nationally significant new utilities connections within the HS4Air route. This would allow important new network connections to be made without need for disruptive additional works. For example, a new below ground National Grid connection could be incorporated into HS4Air using GIL lines.

HS4Air is seen as an example of a more co-ordinated approach to the planning of strategic new infrastructure within the UK. The benefits of this approach include:

  • More benefits from infrastructure projects
  • Better value for investments made in infrastructure
  • Reduced impact on the environment.

For more information contact Alistair Lenczner at alistair.l@expedition.uk.com

Alistair has given an in-depth interview discussing his thinking behind the proposal and hopes for its future development to Global Railway Review.


Download our HS4Air images (1MB PDF)


HS4Air has been featured in the following press articles:

Sunday Express

New Civil Engineer

City AM

Kent Online

Kent Live

International Airport Review

Infrastructure Intelligence

Global Railway Review

West Sussex County Times

Worthing Herald


Spirit FM

Cambridge Network



HS4Air - map showing proposed route
HS4Air - schematic representation of rail services using proposed new high-speed rail line