High-frequency systems with shorter trains are often more effective at moving passengers quickly during peak hours, because the trains come more often, reducing platform overcrowding and wait times. For example, the Tokyo Metro system, despite having relatively shorter trains compared to New York, serves a much higher passenger volume because of its incredibly high frequency and reliability.
New York has some of the longest subways at 600ft (160 meters)
Next up is shanghai and Beijing.
Paris is 6th.
So we could go longer but maybe more frequent is better?
High-frequency systems with shorter trains are often more effective at moving passengers quickly during peak hours, because the trains come more often, reducing platform overcrowding and wait times. For example, the Tokyo Metro system, despite having relatively shorter trains compared to New York, serves a much higher passenger volume because of its incredibly high frequency and reliability.
What I’m thinking is double decker lets people who are going through the downtown (so cities not on the coast) to be out of the way.