The car you board decides your exit — reading a Tokyo platform's floor marks

On a Tokyo platform, the most useful information is under your feet. Painted lines and small tiled numbers mark where each door will open, and if you read them before the train arrives, you can decide something the map never told you: which car puts you closest to the stairs at the far end.

The marks on the ground

Look down where people are already standing and you will see pairs of lines, often in two colours, angled into a lane. These are the seiretsu jōsha (整列乗車) queues — orderly boarding positions, usually one set for the next train and one for the one after. You stand behind the line, let arrivals step off first through the gap in the middle, then file in. Nobody announces this; the floor does.

Choosing a car for the far end

Every car has a jōsha ichi (乗車位置), a boarding position, and at a large interchange the difference between car three and car eight can be a five-minute walk once you arrive. Regular commuters know that at their destination the west stairs sit level with the second door of the front car, so they board there. You can borrow that habit: station signage and the small overhead diagrams near the gates often mark which car lands nearest the exit or transfer you want. Pick the car once, note where the stairs met you, and the next morning you step off into the exit rather than the length of the platform.

The car that isn't yours at rush hour

One position on the floor is not a choice. During the morning peak, one car — usually marked in pink on both the ground and the door — is the josei senyō sha (女性専用車), the women-only car, active only during posted weekday hours. Outside those hours anyone may ride it. The sign states the times in English, so read it rather than guess.

足元の線を見れば、次の電車で並ぶ場所がわかる。

None of this arrives in a rulebook someone handed you. It is written on the platform, in paint and tile, for anyone willing to look down before looking up at the arrivals board.