Air conditioning can be working perfectly on a Polish train and passengers can still feel uncomfortably hot. This summer’s repeated heatwaves have pushed carriages beyond the outdoor temperature limits for which their cooling systems were designed.
Rolling stock is specified for outdoor conditions of up to 35°C, and when the thermometer goes higher, AC equipment continues to operate but can no longer deliver efficient cooling. These are treated as extreme conditions. In Poland, that threshold has been crossed several times this season, which explains the stuffy atmosphere in many compartments despite functioning installations.
The regulatory side offers little support to passengers. The EU’s TSI specification for locomotives and passenger rolling stock defines three temperature classes, but they relate to the expected functionality of the whole train under given external conditions, rather than directly to the air-conditioning system. The European Union does not force carriers to install AC; this depends on agreements between the operator ordering the train and the manufacturer. Poland chooses vehicles in class T2, as Adam Wawrzyniak from PKP Intercity’s management told the parliamentary Infrastructure Commission.
Even the requirements that exist are relative. Regulations do not set a maximum figure for the temperature inside a wagon. They only require a temperature drop of about 6-8°C compared with the outside. At 35°C outside, a wagon could legally remain at 27-29°C. In PKP Intercity’s view, that is still comfortable, although generally accepted comfort levels for closed rooms in summer are 23-26°C, and offices often target 21-23°C.
What the numbers say about the fleet
According to the Rail Transport Office, 77% of multiple units and 75% of carriages running on Poland’s rail network are equipped with air conditioning. Among PKP Intercity’s long-distance fleet, the share is 86%, meaning roughly 200 carriages still lack AC. All of the carrier’s modern types – Pendolino, FLIRT and Dart – are fully air-conditioned.
Technical failures are not behind the complaints. PKP Intercity says that on 30 July, just before the next heat surge, only 30 of its 1,671 carriages had air conditioning faults, i.e. 1.8%. Passengers frequently think they are travelling in a rolling oven, but the blame lies more with design parameters than with defective equipment.
UTK inspectors conducted 235 checks of passenger carriers’ high-temperature preparedness between 2023 and 29 July 2026. The annual figures were 76 in 2023, 79 in 2024, 64 in 2025 and 16 in the incomplete 2026 period. AC-related irregularities totalled 32, including 21 in 2024. Such issues represented 4% of inspections in 2023, 27% in 2024, 9% in 2025 and 13% so far in 2026.
Heat, smarter cooling and future trains
Designing thermal comfort into a train is not easy. A carriage is, in effect, a metal box fighting both frost and sunshine, and the heating or cooling air must be distributed in the right amounts and directions. Polish orders assume solar radiation of 700 W/m², but in late June the Astronomical Observatory of the University of Warsaw measured up to 1,200 W/m². Extreme weather is no longer an anomaly, so rail operators across Europe are being forced to adapt.
Manufacturers can already point to hot-climate experience. Alstom states that its trains are engineered for efficient work from -25°C to +45°C and can be adjusted for tropical or severe winter conditions down to -40°C. The company gives the Riyadh metro as an example, with cooling systems designed for +58°C and even for power supply interruptions.
Cooling consumes energy, and extra cooling or heating means extra costs. Italian researchers writing on sciencedirect.com found that heating, ventilation and air conditioning account for 30% of a train’s total energy demand. With carriers paying more attention to passenger comfort, that demand is set to grow. The same authors tested a passenger-oriented HVAC control method built on a new mathematical model that can incorporate weather data from real routes. In a test on one carriage, it extended thermal comfort by about 1,000 hours and cut annual energy consumption by 27% compared with standard control logic.
Source: WNP.PL, Photo: Shutterstock/Votimedia
