Underground Heat Is a Transit Hazard

Social‑media analysis and temperature records show commuters increasingly complain about excessive heat in subways; complaints rise sharply with small increases in ambient underground temperature, and peak at predictable times tied to crowding and schedules. The finding suggests targeted, time‑bound cooling (fans, ventilation scheduling) can reduce discomfort and energy use, while long‑term design choices (tunnel materials, station ventilation) need updating for a warming climate. — Framing subterranean heat as a discrete urban climate and public‑health problem reframes transit funding, operational priorities, and equity debates about who bears heat risk in cities.