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The “Chūō Line” – A Railway Naming Puzzle for Newcomers in Tokyo 🚃

One of the first things you might find puzzling about Tokyo’s railways when you move here is the way people refer to the “Chūō Line.”

Many people from outside the city know it as the Chūō Main Line (中央本線), a major trunk line about 400 kilometers long that connects Tokyo and Nagoya. With the word “Main Line” in its name, it’s clearly a line of historical significance.

However, in Tokyo, it’s casually called the Chūō Line (中央線)—as if dropping “Main” were completely normal. What’s more, this isn’t just a colloquial nickname. Station signage and onboard announcements officially use “Chūō Line,” with no mention of “Main Line.” It’s no wonder some newcomers find themselves asking, “So… what happened to the ‘Main’ part?” 😅

The reason behind this naming quirk lies in Tokyo’s unique, localized railway distinctions. The orange trains—rapid and special rapid services running from Tokyo Station through Shinjuku, Nakano, Mitaka, and Tachikawa, terminating at Takao—are referred to as the Chūō Line. Technically, this section is known as the Chūō Rapid Line (中央急行線), but that term is rarely used in everyday life.

Beyond Takao Station, toward Yamanashi and Nagano prefectures, lies the portion of the railway typically referred to as the Chūō Main Line. This is where limited express services such as the Azusa and Kaiji operate. Interestingly, some rapid services like the Chūō Special Rapid (中央特快) continue beyond Takao to Ōtsuki, yet they’re still often thought of as part of the Chūō Line rather than the Chūō Main Line.

To add to the confusion, there’s the Chūō-Sōbu Line, best known for its yellow trains. This line connects the Sōbu Main Line and the Chūō Main Line via Akihabara and Ochanomizu, offering all-stop local service between Chiba and Mitaka. Depending on the context, it may be referred to as the Chūō-Sōbu Local Line, Sōbu Line Local, or Chūō Line Local, among other variations.

Here’s an example of how this terminology might appear in train service announcements 📢:

“Service has resumed on the Chūō Line Rapid and the Chūō-Sōbu Line Local, which were temporarily suspended due to a signal failure.”

Each name variation has its own logic based on the line section and type of train, but for first-time passengers, it can feel like navigating a maze of names.

Tokyo’s railways are full of such quirks—things that locals take for granted but may seem strange to newcomers. And in a way, that’s part of what makes this city so endlessly fascinating 😉.

Reference: “Zukai Nemurenaku Naru Hodo Omoshiroi Tetsudō no Hanashi” by Wataru Watanuki (ISBN 978-4-537-22107-7)