Seoul subway congestion, comparison between 2023 and 2025: Which lines increased the most and which lines decreased the most?

How 2023 Compares to 2025

The comparison targets are the 11 routes that are common to the provided CSV. We calculated the simple difference by subtracting the 2023 value from the 2025 value for each route. The overall average increased by 0.8 from 136.2 to 137.0, but the change by route was not in the same direction. This means that even if the averages are almost similar, the movements of each route may vary.

In this article, “increase” and “decline” refer only to changes in the score of the congestion indicator recorded in the data. It does not mean that the number of users has increased or decreased, nor does it determine the cause of the change. The raw data CSV contains only year values ​​for each route, and does not include time zone, station, and traffic information required for cause analysis.

Line 8 had the biggest increase: +20.3 from 139.1 to 159.4.

Line 8 increased by 20.3 from 139.1 in 2023 to 159.4 in 2025. This is an increase of approximately 14.6% compared to the 2023 value. It is also ranked 2nd in the 2025 rankings, 22.4 higher than the overall average of 137.0 at the same time. If you look at the amount of change and the 2025 level together, it is a route worth paying close attention to.

However, a change of +20.3 alone cannot tell us what is causing congestion at a particular station or during a particular commute time. The more immediate conclusion for those using the route is that it is necessary to check the day's guidance and not to schedule transfers in an itinerary that includes Line 8. Statistics are a reference material for determining planning margins, and real-time information is responsible for site selection.

Lines 1 and 2 then rose.

Line 1 showed the second largest increase, rising 17.2 from 109.1 to 126.3. The percentage is about 15.8%. Line 2 rose 6.4 from 144.0 to 150.4, and Line 5 rose 4.1 from 127.2 to 131.3. Line 6 also rose 1.6 from 111.3 to 112.9.

The important thing here is that the increase and the 2025 ranking are not the same thing. Line 1 has risen significantly, but the absolute value in 2025 is 126.3, which is the lowest among the 11. Conversely, Line 9 has the highest value in 2025, but it is lower compared to 2023. This is why changes and levels are viewed together as one table.

Line 4 decreased the most: -22.6 from 166.2 to 143.6.

Line 4 recorded the largest decline, falling 22.6 from 166.2 in 2023 to 143.6 in 2025. The ratio was lowered by about 13.6%. However, the 2025 value of 143.6 is still 6.6 higher than the overall average of 137.0. The fact that it has decreased significantly and the fact that it will remain above average in 2025 are simultaneously established.

Therefore, we should not simply conclude that “Line 4 is less crowded now.” The fact that the year-to-year aggregate results are lower and the congestion at a certain time today are different levels of information. On days when time is critical, such as commuting to work, attending a performance, or traveling to the airport, check real-time route and station announcements just before departure to determine actual train intervals and detour routes.

Line 9, Uisinseol Line, and Sillim Line have been lowered, but the interpretation is different.

Line 9 was lowered by 16.5 from 199.0 to 182.5, and Uisinseol Line was lowered by 8.5 from 161.7 to 153.2. The Sillim line also decreased by 1.5 from 141.9 to 140.4. Line 3 decreased by 9.3 from 140.1 to 130.8, and Line 7 decreased by 11.4 from 152.7 to 141.3.

However, even after being lowered, Line 9's figure is 182.5, the highest among the 11 lines in 2025. In other words, we cannot interpret that “the congestion problem has been solved” just by looking at the decline. Conversely, Line 1 has a large increase, but the absolute value in 2025 is at the bottom. The amount of change should be read separately as a clue to the trend, and the year-to-date figures as a clue to current comparisons.

How to use numbers in your schedule: 3 steps: level, change, and real-time

First, we look at the relative quality of the route in 2025 figures. Second, the direction of change is confirmed by the difference from 2023. Third, right before the actual departure, check the trains and transfers in your time zone in the map app and operating agency information. Of these three steps, the last step is the most important for the actual boarding decision.

For example, for routes that include Line 8, you can start with a little more time by referring to the increase and the top figures for 2025. For routes that include Line 4, the decline should be taken into account, but the above-average figure should be viewed in conjunction with the on-site situation. The point is that data does not automatically determine “route to avoid,” but rather is a tool that allows you more time to prepare.

• 2025 level: Line 9 182.5 is the highest, Line 6 112.9 is the lowest
• Biggest gains: Line 8 +20.3, Line 1 +17.2, Line 2 +6.4
• Biggest drops: Line 4 -22.6, Line 9 -16.5, Line 7 -11.4
• Before actually boarding: First check the real-time route, electronic signboard, and official notices

What cannot be said about this comparison

With only two points in time, it is impossible to know whether it has risen steadily every year, whether it has changed due to a specific event, or which station and time period led to the change. The provided file only has annual values ​​for 2023 and 2025, without intermediate years and detailed distributions. Separate official data and verification are required to attach explanations regarding correlation or cause.

To reproduce, download the same CSV from the original page, subtract 2023 from 2025, and sort in order of the largest difference. Please also remember that the data scope and disclosure values ​​may change, so the figures in this article are based on the provided files checked on August 26, 2026.