Complaints about heating and cooling on Seoul's subway, a recurring summer issue, are expected to surge again this year. Seoul Metro plans to strengthen public guidance and promotion to improve passenger understanding and enhance the efficiency of complaint responses.
According to Seoul Metro on Tuesday, of the approximately 1.01 million total inconvenience complaints received last year, around 790,000 were related to heating and cooling, accounting for 78.4%. While most were complaints about heat, opposing complaints about cold were often filed simultaneously within the same train.
Heating and cooling complaints are particularly concentrated between May and September. With recent climate change driving more heat waves and tropical nights, the volume of complaints has been rising in tandem. In 2024, the national average number of heat wave days reached 24, more than double the average year, while Seoul recorded a record-high 39 tropical nights.
However, in-train climate control is not something crew members can adjust at will. Under Ministry of Environment standards, the system is automatically controlled within a range of 24 to 27 degrees Celsius in summer, with cooling units operating according to the set temperature. This creates a structural limitation in which complaints about heat surge during periods of high passenger density, such as rush hours, while complaints from passengers who feel the cooling too strongly arise at the same time.
An analysis of last year's complaints by time of day showed that heating and cooling grievances were indeed concentrated during commuting hours. More than 70% of "too hot" complaints were filed during these hours, and over half of "too cold" complaints also occurred in the same time slots.
To ease the problem, Seoul Metro plans to step up public guidance. It will expand the placement of information stickers explaining how the heating and cooling system works, currently posted on Lines 2 and 8, to Line 6. The company also plans to display related notices on the complaint reporting screen of the "TTotaApp" to reduce unnecessary complaints.
In addition, the company plans to produce short-form videos explaining the difficulties faced by crew members and the heating and cooling system to raise public understanding. Seoul Metro will also note that the heavy deployment of personnel to handle climate-related complaints can delay responses to emergencies such as medical incidents and crimes.
Technical improvements are also being pursued in parallel. Seoul Metro will pilot an "AI-based cabin temperature control system" on new Line 4 trains, with plans to expand its application going forward. The system predicts congestion in advance and proactively adjusts cooling before trains become crowded.
Passengers are also encouraged to move within cabins or use weak-cooling cars. The center of a cabin generally has higher temperatures, while both ends are relatively cooler. Some lines operate weak-cooling cars set about 1 degree higher than regular cars.
"Train heating and cooling is operated by an automatic control system, so we need passengers' understanding and cooperation," said Ma Hae-geun, head of Seoul Metro's Business Division. "We will continue to make improvements to provide a more comfortable travel environment."
