Should Heathrow Express be absorbed into the Elizabeth Line?

Featured in the Future Transport London Newsletter January 2025 

Direct services on the Elizabeth line between Heathrow, intermediate West London stations, Paddington, 22 other stations across Central London and beyond were introduced on 24th May 2022. Office of Road & Rail data shows 5.8 million passengers used HEX in Financial Year 2019-20 and 4.5 million (on average, only 82 passengers per train) during 2023-24, a drop of 22%, despite relentless marketing. By contrast, TfL now wishes to double its two trains per hour (tph) Elizabeth line service to Terminal 5 but cannot easily do so, for reasons explained below.

The current contract to operate the Heathrow Express (HEX) runs from 2018 to 2028. Should HEX then be absorbed into the Elizabeth line, to reduce the imbalance between its western and eastern branches, to grow demand and to increase the public transport share of Heathrow surface access above the current 39 per cent?

Since opening in 1998, HEX has provided a 15-minute journey time and a 15-minute frequency between the airport’s central area and Paddington but serves only that one station in Central London. In the early years, it was possible to check in for your flight and to drop off your baggage at Paddington, but the facility was under-used and discontinued for cost reasons in 2003. The HEX service was extended to Terminal 5 when that opened in 2008.

The current HEX trains have a top speed of 110 mph and share the busy Great Western (GW) main line with Intercity trains between two dedicated platforms (6 and 7) at Paddington and Airport Junction.

The Elizabeth line shares the busy GW relief line with freight trains and operates four tph to Terminal 4 (connecting with HEX) as well as two tph to Terminal 5. TfL now wishes to double the frequency but the necessary timetable ‘paths’ are elusive. Journey time between Paddington and the airport central area is around half an hour, depending on time of day and stopping pattern at intermediate stations.

Some of the many Elizabeth line services which currently reverse at Paddington are due to be extended to Old Oak Common station when it opens; additional trains are on order. HEX trains are also planned to call at Old Oak Common, so they would no longer be able to achieve their 15-minute journey times between Paddington and the airport Central area.

If it is decided to absorb HEX into the Elizabeth line, all trains destined for Heathrow, whether express or stopping, would then depart from the same Elizabeth line platform at Paddington and at the 22 stations east of it, giving passengers more frequency. If an express service survives, premium fares could still be charged (as is customary on railair links around the world) but first class and toilets would disappear. Elizabeth line trains have generous floorspace which can be used for standing, luggage, pushchairs and wheelchairs in any combination as required. 

Two platforms at Brunel’s magnificent London terminus would then be vacated: no doubt they could be put to excellent alternative use. 

However, it is unclear whether it would be better to schedule the additional four Elizabeth line trains per hour on the GW relief line or on the main line to/from Heathrow (both operate near full capacity). If the latter, trains would have to cross over to/from the Relief Line and use their performance characteristics, including a top speed of over 100 mph, to avoid delaying Intercity services. The vicinity of Old Oak Common station might be the best location for crossing over ‘on the flat’ (to avoid the expense of grade separation) and the track layout there could be designed accordingly.

Neil Roth