3 ms·

The problem with subway speed is not top speed, it's maximum acceleration. There is a maximum acceleration (and deceleration) above which the metro is uncomfort

The problem with subway speed is not top speed, it's maximum acceleration. There is a maximum acceleration (and deceleration) above which the metro is uncomfortable or even dangerous to its users, some of which are going to be standing. Since the speed at stations has to be zero, this automatically limits your top speed unless you make the stop farther apart, which then comes with other downsides. A 60 mph metro doesn't really make sense so you can't compare that to the speed of NYC subways, however in Paris there are already two separate systems (completely integrated though): the metro with short stops and the RER with longer sections. The RER already goes to 100 km/h within Paris, it moves about 3 million passengers per day, on regular rails (the RER A line is the rail line with the most traffic in Europe).

melling 9y ago
What is that maximum acceleration? You’re doing a bit of hand waving. There are express subway stops in Manhattan, for example. Also consider there’s much less noise and a much smoother ride on the maglev.
- seszett 9y ago
  I don't know what are express subway stops in NYC and if they have a higher top speed than regular subway cars, but I doubt it unless they have separate tracks - they might be faster by skipping stations but that's unrelated to the topic. I'm not saying it doesn't exist anywhere outside Paris anyway, just that it already exists outside Beijing. I'd expect London to have a similar system, too. https://link.springer.com/article/10.1007/s40864-015-0012-y https://link.springer.com/article/10.1007/s40864-015-0012-y says about 1.5 m/s² is the maximum acceptable acceleration rate for passengers. My local metro in Lille uses 1.3 m/s² and I find it barely acceptable. But that is only acceptable anyway over a short time, and for a trip under continuous acceleration/deceleration it should stay under at most 0.5 m/s². I'll let you do the math for how many seconds you can gain on a 500 m stretch between metro stations. Also, RER or TGV lines are really just as smooth as the maglev I have used in Incheon. Rail is very smooth and quiet on modern continuous welded rail. On TGVs on dedicated lines you usually don't notice when the train starts.

melling 9y ago

What is that maximum acceleration? You’re doing a bit of hand waving. There are express subway stops in Manhattan, for example. Also consider there’s much less noise and a much smoother ride on the maglev.

seszett 9y ago
I don't know what are express subway stops in NYC and if they have a higher top speed than regular subway cars, but I doubt it unless they have separate tracks - they might be faster by skipping stations but that's unrelated to the topic. I'm not saying it doesn't exist anywhere outside Paris anyway, just that it already exists outside Beijing. I'd expect London to have a similar system, too. https://link.springer.com/article/10.1007/s40864-015-0012-y https://link.springer.com/article/10.1007/s40864-015-0012-y says about 1.5 m/s² is the maximum acceptable acceleration rate for passengers. My local metro in Lille uses 1.3 m/s² and I find it barely acceptable. But that is only acceptable anyway over a short time, and for a trip under continuous acceleration/deceleration it should stay under at most 0.5 m/s². I'll let you do the math for how many seconds you can gain on a 500 m stretch between metro stations. Also, RER or TGV lines are really just as smooth as the maglev I have used in Incheon. Rail is very smooth and quiet on modern continuous welded rail. On TGVs on dedicated lines you usually don't notice when the train starts.