The amount of time subway trains stop in stations varies with the station. Generally speaking, the time corresponds to what the transit company considers as optimal value. There is a strong correlation between the size or the importance of the station to the network and the time a train stays at the platform. So far, I have identified three classes of stations. The classification may vary with the network operator, so it should be taken with a grain of salt:
- ordinary or simple stations, with a wait time of 10 sec
- connected stations, with a higher wait time, between 20-30 sec
- major stations, where wait times range between 40-60 sec, and could occasionally go beyond the minute limit.
The size of the station determines the number of street level entries and limits the total capacity of the station. The connected stations and the hub stations will play a major role in the future of the smart cities. In this case we are talking about multi modal nodes.
Ordinary stations are the majority. They cover most of the needs of the people.The small station near your home, or the station where you get off to go to the market. An ordinary station has a few street level entries. The real minor stations have a single entry. Most of the time, ordinary stations have two entries, each corresponding to one end of the subway level platform. Recently, new standards require the station to have two regular entries plus one or two special entries (elevators).
From a historical point of view, most subway networks have started with one line having only ordinary stations. Normally, the forks or line splits do not require special entry infrastructures. In the example above, the green line is the oldest subway line in town. Most of the stations on the green line are ordinary.
Connected stations can have up to 3 different lines. More than that and the size of the station increases substantially, because of the depth limitations of the subway. To my knowledge, there are no subway stations with four stacked levels of subway tunnels. suburban trains circulating at bigger depths are not included here.
From a historical point of view, when a second line is added to the network, there is one station where the two lines connect. In some cases, two lines may share several stations. In some cases, a network can have two semi-circular lines that meet at both of their ends.
The best example of lines with connected stations is in Paris, where lines 8 and 9 share several stations. In our example, the green line and the eggplant line connect in two places.
Major stations or hubs are important parts of the transportation network, where many subway lines can intersect. The station can harbor railway stations or suburban train stations. These are very important stations. In most of the cases the hubs connect subway lines with railway lines. Historically, every city developed a hub station at the central railway station. In our case, we see that there is a hub where the red and the eggplant line meet the two brown railway lines.