Other's have said maintenance, which is right. But the context is also important in that if the trains are delayed by 5 minutes in Tokyo at peak hours, the cong

Other's have said maintenance, which is right. But the context is also important in that if the trains are delayed by 5 minutes in Tokyo at peak hours, the congestion can be so bad that many people won't even fit in the next train. This can have a cascading effect, and since so many use the public transport, opting for car is not a workable solution in such density. So it actually makes sense to focus on efficiency and reliability at peak hours, at the cost of running it 24hours. Tokyos rail line are one of the few trains in the world that actually make profit (although not all of it from trains) and reliability is kinda key to this profit margin, especially at prime time. (Most major stations have malls and commercial activities in Japan. And those are run by the train companies, and surprisingly the majority of the profit for Train companies are not the trains but those activities. Those are not open past 22:00 in most places, so that's another reason) Edit: Not just bike mentioned it on this video (timestamp) https://youtu.be/6dKiEY0UOtA?t=887 https://youtu.be/6dKiEY0UOtA?t=887