4 ms·

Maglev trains can start and stop much, much faster than regular trains.

JumpCrisscross 5y ago
> Maglev trains can start and stop much, much faster than regular trains Ah, wasn't aware of that. Thank you.
jcranmer 5y ago
Conventional trains' acceleration profiles are already limited by passenger comfort rather than engineering difficulties. Being able to start and stop much faster isn't helpful if it's already outside maximum operating guidelines.
- sudosysgen 5y ago
  I was under the impression this wasn't the case. Passenger planes accelerate at around 3.5m/s/s. That's 100km/h every six seconds.
  - jcranmer 5y ago
    And when planes take off, all the passengers and crew are seated in seats with fastened belts, all luggage is stowed, and tray tables are closed. By contrast, when a train departs a station, there are frequently passengers who are still roaming the aisle with their luggage. And I might have a cup of coffee or something sitting on the table in front of me (or behind me, from the perspective of the train's direction of acceleration).
    - sudosysgen 5y ago
      Of course, you shouldn't have people roam in the aisle if you want to accelerate faster. If you're seriously considering rail as an alternative to airtravel, and at 600km/h you are, then having people stow their luggage and sit down is not a serious issue. For the sake of comparison - a Toyota Corolla will do 100km/h/6s. You don't need to fully stow your cargo, you just need not to have drinks on the table. Even standing you would be fine, though there is some danger you'd trip. Beyond that, buses see accelerations on the order of ~0.2G often, and that's with people standing up, in an unpredictable fashion.
      - jcranmer 5y ago
        The root context of this discussion is basically whether or not it makes sense to add in intermediary stops on a rail line. If you're insisting that people have to be seated and have no drinks out for every intermediate stop, that rather sharply raises the discomfort level of stops. Another unpredictable element of train acceleration is the need to slow down to negotiate a curve, which isn't necessarily the case only in the immediate vicinity of a station. FWIW, the numbers I generally see bandied about for acceleration on (decent) trains is about 1 m/s^2.
        sudosysgen 5y ago
        The "intermediate stop" being mentioned was Philadelphia. I don't think asking people to be seated for 45 seconds before and after each stop adds that much discomfort. 0.1g is the acceptable lateral acceleration when standing up without bracing. (https://link.springer.com/article/10.1007/s40864-015-0012-y https://link.springer.com/article/10.1007/s40864-015-0012-y) If you get caught standing up, even 3.5 m/s/s is not dangerous. It is uncomfortable, but in a high speed train you are expected to be sitting down. Also you wouldn't need to put drinks away. As I said, that's the acceleration of a Toyota Corolla. You would need the drinks to be covered though. The limiting factor in longitudinal acceleration in trains is that we expect people to be standing up for the whole trip. This isn't the case in a high speed train. As for curves - the solution is not to go through any sharp curves unless you are already close to a stop and would have to slow down anyways.
      - Symbiote 5y ago
        There's not much point accelerating faster if it means waiting longer so everyone can find a seat. Perhaps this would be interesting to you, "Passenger Stability Within Moving Railway Vehicles: Limits on Maximum Longitudinal Acceleration". https://link.springer.com/article/10.1007/s40864-015-0012-y https://link.springer.com/article/10.1007/s40864-015-0012-y
        sudosysgen 5y ago
        I have actually read the study and linked to it in another comment. You don't need to wait for everyone to be seated. You're not going to fall over at 0.2G or 0.3G, it will just be uncomfortable. But you should plan for everyone to be able to find a seat.

> Maglev trains can start and stop much, much faster than regular trains Ah, wasn't aware of that. Thank you.

Conventional trains' acceleration profiles are already limited by passenger comfort rather than engineering difficulties. Being able to start and stop much faster isn't helpful if it's already outside maximum operating guidelines.

sudosysgen 5y ago
I was under the impression this wasn't the case. Passenger planes accelerate at around 3.5m/s/s. That's 100km/h every six seconds.
- jcranmer 5y ago
  And when planes take off, all the passengers and crew are seated in seats with fastened belts, all luggage is stowed, and tray tables are closed. By contrast, when a train departs a station, there are frequently passengers who are still roaming the aisle with their luggage. And I might have a cup of coffee or something sitting on the table in front of me (or behind me, from the perspective of the train's direction of acceleration).
  - sudosysgen 5y ago
    Of course, you shouldn't have people roam in the aisle if you want to accelerate faster. If you're seriously considering rail as an alternative to airtravel, and at 600km/h you are, then having people stow their luggage and sit down is not a serious issue. For the sake of comparison - a Toyota Corolla will do 100km/h/6s. You don't need to fully stow your cargo, you just need not to have drinks on the table. Even standing you would be fine, though there is some danger you'd trip. Beyond that, buses see accelerations on the order of ~0.2G often, and that's with people standing up, in an unpredictable fashion.
    - jcranmer 5y ago
      The root context of this discussion is basically whether or not it makes sense to add in intermediary stops on a rail line. If you're insisting that people have to be seated and have no drinks out for every intermediate stop, that rather sharply raises the discomfort level of stops. Another unpredictable element of train acceleration is the need to slow down to negotiate a curve, which isn't necessarily the case only in the immediate vicinity of a station. FWIW, the numbers I generally see bandied about for acceleration on (decent) trains is about 1 m/s^2.
      - sudosysgen 5y ago
        The "intermediate stop" being mentioned was Philadelphia. I don't think asking people to be seated for 45 seconds before and after each stop adds that much discomfort. 0.1g is the acceptable lateral acceleration when standing up without bracing. (https://link.springer.com/article/10.1007/s40864-015-0012-y https://link.springer.com/article/10.1007/s40864-015-0012-y) If you get caught standing up, even 3.5 m/s/s is not dangerous. It is uncomfortable, but in a high speed train you are expected to be sitting down. Also you wouldn't need to put drinks away. As I said, that's the acceleration of a Toyota Corolla. You would need the drinks to be covered though. The limiting factor in longitudinal acceleration in trains is that we expect people to be standing up for the whole trip. This isn't the case in a high speed train. As for curves - the solution is not to go through any sharp curves unless you are already close to a stop and would have to slow down anyways.
    - Symbiote 5y ago
      There's not much point accelerating faster if it means waiting longer so everyone can find a seat. Perhaps this would be interesting to you, "Passenger Stability Within Moving Railway Vehicles: Limits on Maximum Longitudinal Acceleration". https://link.springer.com/article/10.1007/s40864-015-0012-y https://link.springer.com/article/10.1007/s40864-015-0012-y
      - sudosysgen 5y ago
        I have actually read the study and linked to it in another comment. You don't need to wait for everyone to be seated. You're not going to fall over at 0.2G or 0.3G, it will just be uncomfortable. But you should plan for everyone to be able to find a seat.