As the United Kingdom experiences its third heatwave of the year with temperatures exceeding 30°C, passengers are seeking relief from the sweltering conditions, highlighting a significant disparity in air conditioning availability across the nation's rail network. The London Underground, in particular, has not introduced a new air-conditioned train in nearly a decade, with the most recent additions rolling out in June 2017.
Approximately 190 London Underground trains are equipped with air conditioning, but these are limited to shallow lines. Deep-level lines, such as the Bakerloo and Piccadilly lines, which form the majority of the network, still lack this feature. Transport for London attributes this to the constraints of narrow, Victorian-era tunnels, which offer limited space for cooling equipment on the exterior of carriages. However, upgrades are underway, with the Piccadilly line slated to receive new trains built by Siemens later this year, featuring compact under-carriage air conditioning units. London TravelWatch noted that these new trains, not expected until December, are urgently needed.
Across other UK train operators, air conditioning is more prevalent. Chiltern Railways' Chiltern Explorer fleet, launched in January, features automatic onboard air conditioning that adjusts to outdoor temperatures. South Western Railway states that most of its trains are air-conditioned, with new Arterio trains launched in 2024 also equipped with the technology. Avanti West Coast reports that all of its trains are fitted with air conditioning and undergo regular maintenance, utilizing remote HVAC data to preemptively address issues. Greater Anglia confirmed that all of its trains, serving London and the east of England, are equipped with both air conditioning and heating systems. Great Western Railway's fleet either has air conditioning or relies on ventilation through openable windows and extractor fans. London North Eastern Railway (LNER) trains are equipped with individual air conditioning units and a ventilation system providing a continuous flow of fresh air. Thameslink's services primarily use trains with air conditioning, with plans to introduce more new air-conditioned trains over the next two years. The Elizabeth line, which opened in May 2022, features fully air-conditioned carriages.
