'Big Star Teacher' shocked by Seoul's Line 9 'hell train': 'Crushing pressure, rain, humidity, sweat pouring down'

Choi Tae-sung, the Korean history lecturer widely known by his nickname "Big Star Teacher," shared his firsthand experience riding Seoul Subway Line 9 during the morning rush hour — and came away stunned by the notorious "hell train."

Choi took to his social media account Wednesday morning to describe the commute, writing: "A morning on Line 9 that makes me bow my head in respect to every working person in this country."

Alongside a photo of the packed train interior, he wrote: "Wow, Line 9 at 8 a.m. — hell train. The pressure is closing in, the rain is coming down, it's humid, sweat is pouring like rain. I'm worn out before the day even starts."

He added: "The monsoon rain was streaming down, the world was soaked with humidity, and I was dripping with sweat. I hate getting my shoes wet so much that I was dreading stepping outside after getting off the subway — I ended up switching to rain boots."

After arriving at the broadcasting station, he ordered an iced Americano. "Why does it taste so good?" he wrote. "Now I'm getting back on Line 9 to Seoul Station to go give a lecture in Busan. This is life. Everyone, hang in there — Wednesday, July 8."

Line 9, the route Choi rode, is widely regarded as one of the most severely congested lines on the Seoul subway network, drawing persistent complaints from commuters.

A probe found that congestion at Noryangjin Station on Line 9 reaches 182.5% during morning peak hours. A rate of 100% means a train is at full capacity, while anything above 150% is classified as a crush-loaded state — a level that raises fears of crowd crush injuries.

Peak congestion on Line 9 express trains hit as high as 199% as of late 2023.

The line's reputation as a "hell train" is largely attributed to a failure in demand forecasting from the outset.

While most Seoul subway lines were designed to accommodate eight to 10 cars, Line 9 was built from the outset for only six. Expanding to eight cars would require lengthening station platforms — an undertaking that would demand astronomical costs and force service suspensions to demolish and rebuild the platforms.

The problem has been compounded by surging demand driven by population growth tied to new town development in Gimpo, making congestion relief on Line 9 an increasingly intractable challenge.

In response, the Seoul Metropolitan Government last month announced a plan to overhaul the city's subway operations through signal system upgrades, moving away from piecemeal fixes such as adding cars, expanding express services or building new lines. The plan calls for the phased introduction of a state-of-the-art communications-based train control system to cut average congestion by more than 20 percent.

The initiative involves switching the subway signaling system from the conventional track-circuit method to a wireless communications-based system. Seoul city officials said the change would dramatically reduce train headways, boosting transport capacity by about 20 percent and easing crowding.

The city plans to apply the new system first to the Ui-Sinseol Line, where congestion exceeds 160 percent, before rolling it out in stages to Line 9 and Line 2.