A Comprehensive Guide to Seoul Subway Line 4
Seoul Subway Line 4 is a vital artery of the Seoul Metropolitan Subway system, stretching across the metropolitan area from the southwest to the northeast. Serving as a critical link for commuters, this long-distance rapid transit line connects diverse regions, including Seoul, Gyeonggi-do, and Namyangju-si. Whether you are traveling through the heart of Seoul or heading toward the coastal areas of Siheung, Line 4 provides extensive coverage and essential connectivity.
The line is characterized by its multi-operator structure. The central section within Seoul is operated by Seoul Metro, while portions of the line offer through-service to Korail's Ansan and Gwacheon Lines. Additionally, the northernmost section, known as the Jinjeop Line, is owned by a company under Namyangju-si, with operations contracted to Seoul Metro.
![Seoul Metro 4000 series EMU in July 2023]
Key Facts
- Total Length: Approximately 85.7 km (53.3 mi)
- Termini: Jinjeop (North) to Oido (South)
- Daily Ridership: 790,915 passengers (2024 data)
- Operating Speed: Up to 100 km/h (62 mph)
- Electrification: Dual system using 1,500 V DC and 25 kV AC
Technical Specifications and Operations
Line 4 is a complex engineering feat that utilizes different electrification methods depending on the section. From Jinjeop to Namtaeryeong, the line operates on 1,500 V DC (Direct Current). However, from Seonbawi to Oido, the system switches to 25 kV AC (Alternating Current) at 60 Hz. This transition occurs at a specialized flying crossover point between Namtaeryeong and Seonbawi stations.
Service Types
Most passengers utilize the standard rapid transit service, which stops at every station. However, during weekday rush hours, an Express train service is available to reduce travel times. The express service follows a specific pattern:
- It stops at all stations between Danggogae and Sanbon.
- It then makes strategic stops at Sangnoksu, Jungang, Choji, Ansan, Jeongwang, and Oido.
Station Signage and Design
The station signs on Line 4 feature a unique, oblong, "squashed" design. The station number is positioned on the left side within a pill-shaped graphic, while the station name is displayed in the center-right in three formats: Hangul, English, and Hanja (Chinese characters), listed from top to bottom. Two arms extend from the sides of the sign to indicate the direction of travel and the names of the adjacent stations.
![Korail Class 341000 series EMU in April 2020]
Historical Development
Since its inception, Line 4 has undergone several major expansions to meet the growing needs of the metropolitan population. The line officially opened on April 20, 1985, initially running from Sanggye to Sadang.
Timeline of Major Milestones
- 1993: The line was extended northward to Danggogae and southward to Namtaeryeong.
- 1994: The southward extension reached Ansan via the Gwacheon Line section.
- 2000: The line was extended westward from Ansan to Oido.
- 2017: Express services were extended to reach Oido.
- 2022: The Jinjeop Line opened, extending the service from Buramsan (formerly Danggogae) to Jinjeop.
Ridership Trends
Line 4 has seen significant fluctuations in usage over the decades. While the line reached a record high in 2016, it experienced a dip during the COVID-19 pandemic. However, the opening of the Jinjeop Line in 2022 helped drive ridership back up. In 2024, the line recorded an annual ridership of 289.47 million passengers.
| Year | Annual Ridership | Change (%) | Notes |
|---|---|---|---|
| 2024 | 289,474,890 | 3.7% | - |
| 2022 | 248,951,000 | 13.4% | Jinjeop Line expansion |
| 2020 | 222,536,000 | 31.9% | COVID-19 pandemic |
| 2016 | 346,954,000 | 14.7% | Highest on record |
| 2010 | 303,625,000 | 2.2% | - |
Frequently Asked Questions
What are the endpoints of Line 4?
The northern terminus is Jinjeop (in Namyangju-si), and the southern terminus is Oido (in Siheung City).
How does the express service work?
The express service operates only during weekday rush hours. It skips certain stations between Sanbon and Oido to provide faster transit for long-distance commuters.
Which companies operate Line 4?
The line is operated by a combination of Seoul Metro, Korail, and the Namyangju City Urban Corporation.
Does the train change power sources?
Yes. Because different sections of the line use different electrical systems, the trains switch between 1,500 V DC and 25 kV AC at the Namtaeryeong–Seonbawi section.
Where can I transfer to other lines?
Line 4 offers numerous transfer points, including Dongdaemun History & Culture Park (Line 2), Chungmuro (Line 3), Seoul Station (Line 1), and Hanyang Univ. at Ansan (Suin–Bundang Line).