Well, I did say "as far as I know." I was pretty sure the Toei website said that it had the monorail. Unless there is more than one monorail...

A track is 1 one side traffic lane.
There is not a place letting a vehicle evacuate.
There is not time to maintain it.
A motor carrier and the taxi company which are half-dead go bankrupt.
The subway is far from the residential area.
A subway company is unprofitable.
The aggravation of the peace and order is expected.
A businessman in further Hell !!! (Overtime work increases)

There are the problems in various ways

Yes they run the Ueno Zoo monorail, 2 stations that connect one end to the other in 90 seconds.

There are three monorails in Tokyo.
1. Ueno Zoo Monorail (Toei operated, two stations, but a monorail nevertheless)
2. Tokyo Monorail (Connecting Haneda Airport, private company)
3. The Tama Monorail, operating out in Western Tokyo around Tachikawa. (private company)

naruhodo...

I'm a westie, Tokyo is just a sometimes vacation spot for me. I don't know it like I know Kansai.

It's no problem, I'm no expert on the trains out there in the West.

There are usually pros and cons to every decision .......and the same applies to running the subway system 24 hours a day. Looking at the positive side, surely a city like Tokyo should be more 24 hour friendly. Not all people can afford to take a taxi home after drinking late into the night, and why not give people the option to take the train or a taxi. If some people miss the last trian they go to all night karaoke rooms or bars, or stay in the late night izakayas. Wouldn't it be better to give these people an option of when they can go home. Look how packed the last trains are .........that seems to show that people would be happy to take trains later than the last train. Why not give people the choice?