How can more Elizabeth line services be run to Heathrow?

Featured in the Future Transport London Newsletter May 2025

Neil Roth’s January article asks if Heathrow Express should be absorbed into the Elizabeth line. The answer is probably yes, but depends, inter alia, on whether, and at what fare, Heathrow Express can continue to attract passengers; demand growth at Heathrow and elsewhere; and the extent to which the Elizabeth line could cope with longer trains, more frequent services, or new infrastructure.

Heathrow Express passenger numbers peaked at 6.3 million but were down to 4.1 million in 2024. Fewer passengers are willing to change at Paddington when the Elizabeth line has a through service. For journeys booked more than 45 days in advance, Heathrow Express now offers an Advance £10 Ticket, cheaper than via the Elizabeth line through Paddington to Zones 1 or 2. As Neil says, TfL would already like to increase Elizabeth line services from six to eight per hour, four each to Terminal 4 and Terminal 5.

Demand on the Elizabeth line is still growing. Passenger numbers at Heathrow are back above pre-pandemic levels and, even within the current cap on aircraft movements, both load factors and aircraft size can continue to rise. Around Elizabeth line stations, housing is appearing and more is being planned. Old Oak Common will add passengers from HS2 ‘after 2029-2033’ until at least 2040. It may be the late 2030s before we know how the Elizabeth line copes, or whether stopping all Main Line trains at Old Oak Common provides material relief. If Elizabeth line services from Heathrow and the west reach Old Oak Common already busy or full, passengers from HS2 may prefer to wait for a train which starts there empty.

Longer Elizabeth line trains would add capacity, and the new platforms in the core have provision for extension from 9-car/205 metres to 11-car/250 metres. However, platforms at Heathrow are only 203-217 metres long and could need major work to handle longer trains.

More frequent Elizabeth line trains are possible, with scope to increase services through the core from 24 to 30 trains per hour, probably the upper limit of what could be operated, particularly as visitors with baggage may slow boarding and alighting times. However, operating more trains in the core would not create more paths west of Old Oak Common.

There has long been talk of six-tracking at least some of the Great Western Main Line. It is difficult to see how this could be done quickly, but the most pressing need seems likely to be between Acton West, where freight joins Elizabeth line services on the Relief Lines, and Airport Junction. If Main Line services could be put in tunnel between east of Acton West and west of Airport Junction, Elizabeth line trains could also operate on the Main Lines with limited stops, such as at Ealing Broadway and Hayes & Harlington, which already have Main Line platforms.

Where could the portals for the Main Line tunnels be? West of Airport Junction, there is open land between Iver and Langley, where the proposed Western Rail Link to Heathrow (WRLTH) would emerge. East of Acton West is much more built up, but the Main Lines are already being spread at Old Oak Common to create four platforms on two islands. There is a growing suspicion that they will be used by too few people to justify the cost and time required to stop and restart every train. Perhaps the inner two should be closed, or ideally never built, and the space between them used as a ramp down to a new tunnel?

Dick Dunmore