Seoul Metro announced on the 22nd that it will strengthen public guidance and promotion in preparation for an increase in complaints about subway heating and cooling during the summer. The agency plans to make the operating principles of the heating and cooling system easier to understand while also improving its ability to respond to urgent complaints.
Last year, Seoul Metro received a total of slightly over 1.01 million complaints about subway inconveniences. Of those, about 790,000 were related to heating and cooling, accounting for 78.4% of the total. Most of them were complaints that it was “too hot.”
Heating and cooling complaints come in clusters from May to September, when the weather gets hotter. As climate change lengthens and intensifies summer heat waves, related complaints are also on the rise. According to the Korea Meteorological Administration, the national average number of heat-wave days in the summer of 2024 was 24.0 days, 2.3 times the normal annual average of 10.6 days from 1991 to 2020. Seoul also recorded 39 tropical nights that year, the most ever.
◆ Train air conditioners cannot be adjusted by crew members
One common misunderstanding among passengers is that crew members directly control the train’s air conditioning.
In fact, train heating and cooling are automatically operated at 24 degrees Celsius in summer and 18 degrees Celsius in winter in accordance with the Ministry of Environment’s notice. Because the system automatically runs to match the set standard temperature, crew members cannot arbitrarily raise or lower the temperature.
Because of this structure, there are limits to lowering the temperature significantly in just one car. During crowded rush hours, complaints that it is too hot concentrate as passengers pack into trains, but complaints that it is too cold also come in from passengers who feel the cooling is excessive.
According to Seoul Metro’s analysis of last year’s complaints by time of day, complaints were concentrated between 7 a.m. and 9 a.m. and between 6 p.m. and 8 p.m. More than 540,000 “too hot” complaints, or 72.8% of the total, and 27,720 “too cold” complaints, or 57.3% of the total, were received during those two time periods. Seoul Metro said the difference in perceived temperature depends on train crowding, clothing, health condition, and time of boarding.
As conflicting complaints come in simultaneously from the same car, the burden on call center counselors and train crew also increases. The agency explained that if time is consumed handling heating and cooling complaints, it could interfere with responses to urgent complaints such as medical emergencies or crime reports.
◆ Expanded guidance and pilot introduction of an “AI temperature control” system
The agency has begun strengthening guidance to help citizens understand the system. It will expand heating and cooling 안내 stickers, which were attached to Line 2 and Line 8 last year, to Line 6 as well.
In addition, a notice will be displayed at the top of the complaint screen in the “Ttota app,” where more than 70% of complaints are filed, informing users that responses to urgent complaints may be delayed while heating and cooling complaints are being handled. Seoul Metro also plans to produce a short video explaining the automated control system and including the hardships of crew members.
Technical improvements will also be pursued in parallel. Starting in the last week of May, Seoul Metro will pilot an “AI cabin optimal temperature control system” on one new train set on Line 4, then gradually expand the system to 25 new train sets on Line 4.
The system uses AI-based congestion forecasts learned in advance to adjust cooling before a train enters a crowded section. In April, it won the grand prize at a Seoul City creative presentation event in recognition of its effectiveness in improving the cabin environment. Trains leaving depots during rush hours are keeping both cooling and ventilation fans running continuously.
There are also methods passengers can use right away. Since the center of a car tends to be warmest and the ends coolest due to the flow of cold air, moving to the end of the car can help if you feel hot. Passengers who are sensitive to cold can use the mildly cooled cars, which are operated at 1 degree Celsius warmer than regular cars.
The mildly cooled cars are located in the 4th and 7th cars on Lines 1, 3, and 4; the 4th and 5th cars on Lines 5, 6, and 7; and the 3rd and 4th cars on Line 8. Line 2 does not operate mildly cooled cars because of its high congestion levels.
“Train heating and cooling are automatically controlled according to Ministry of Environment standards, and all departments are cooperating to ensure a comfortable riding environment,” said Ma Hae-geun, head of Seoul Metro’s business division. “Since crew members cannot arbitrarily adjust cooling, we ask for citizens’ understanding and cooperation so that urgent complaints such as medical emergencies or crimes can be handled first.”