AREX from ICN to Gimpo, then Line 9 express to Gangnam
From T1/T2, ride the AREX all-stop train to Gimpo Airport, then transfer to Seoul Subway Line 9 toward Yeouido or Gangnam. Total ICN–Gangnam corridor time usually lands around 60–75 minutes if you catch a Line 9 express. Fares sit in the $3–4 range using a single T-money or credit card tap across both AREX and Line 9.
AREX all-stop trains from T1 and T2 run every few minutes most of the day, then Line 9 trains show up every 5–8 minutes, with expresses typically every 10–20 minutes. This combo works well if you’re staying near Yeouido, Dangsan, Express Bus Terminal, Sinnonhyeon, or Seocho along Line 9. One Reddit user flat-out said, “AREX to Gimpo then Line 9 express is usually faster than airport buses in traffic” for Gangnam runs.
The real trick: only some Line 9 trains are express between Gimpo and stations like Yeouido and Express Bus Terminal. Miss the express and take a local, and your ICN–Gangnam time can stretch well beyond 75 minutes. Station boards mark “express” (급행) vs “local” (일반), and Naver Map will show the next express departure down to the minute so you can decide if waiting 10–15 minutes is worth it.
Crowding is the tax you pay for the low $3–4 fare. Line 9 has a bad reputation between Gimpo and Express Bus Terminal, with commuters on r/korea calling it “the worst” line during the 7:30–9:30 and 17:30–19:30 peaks. One regular warned that Line 9 “can be hell with luggage at rush hour,” especially when boarding at Gimpo with big checked bags.
The transfer at Gimpo is also not a quick hop. From the AREX platform to Line 9 you walk through long underground corridors, including several sets of escalators and some gentle ramps, which can eat 8–12 minutes with bags. Elevators exist but can have visible queues of 10–20 people at busy times, so factor that in if you have a stroller or two large suitcases.
Regulars game the system. Many will check Naver Map: if the next Line 9 express from Gimpo is 18–20 minutes out, they sometimes stay on the AREX to Seoul Station and switch to Lines 1, 4, 5, or 6 instead. Others line up at the far ends of the Line 9 platform where cars board a bit lighter and where elevators sit closer to the exits at Yeouido or Express Bus Terminal.
Practical tip: Landing in T1 or T2 between 7:30–9:30 or 17:30–19:30 with big luggage? Skip Line 9 and take an airport limousine bus to Gangnam; outside those windows, AREX + Line 9 express is usually the cheapest 60–75 minute play.