Overview
- Vienna says about three in four trips are now on climate‑controlled vehicles and will add an ice‑cube symbol in the WienMobil app from early July to show which trains are cooled.
- Hamburg operators report most buses are air‑conditioned but many older U‑ and S‑Bahn trains lack AC and cannot be retrofitted because of vehicle design and weight limits.
- A MOPO temperature test recorded roughly 36°C inside an S‑Bahn carriage, illustrating how interior heat can exceed outside temperatures and worsen passenger discomfort.
- Operators say air conditioning uses substantial vehicle energy—about one‑sixth on some trains—and maintenance and depot access limits mean trains will often run even when AC systems fail to keep service punctual.
- Full fleet cooling will be gradual and costly, so cities are prioritizing cooled procurement, app tools and targeted retrofits while passengers face uneven comfort and potential health risks during heat waves.