Quote:
Originally Posted by logan5
The distance between trains is required because of dwell times. You think Skytrain vehicles are separated by 90 seconds or more because that's how much breaking distance they need?
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I'm
not talking about train frequencies, I'm talking about
minimum safe distance between trains. For example, watch the behaviour of trainsets that are returning to the OMC at the end of the day. They bunch up behind revenue trains because the revenue trains stop at stations while they don't.
The out-of-service train will gradually slow down and stop somewhere around 100 feet back from the revenue train while it stands in the station, and then it will follow at a distance which increases as the trains accelerate. That distance is governed by a the "
moving block" that the automated control system places around every trainset. The block is large enough so that if the leading train were to somehow come to a worst-case abrupt stop (as trains have done in the past due to broken power pickup shoes, for example) the following train has enough room to come to a safe stop.
For a trainset operating at, say 80km/h, that minimum allowed distance between it and the trainset ahead of it is basically the same distance that a car is
supposed to be following it's lead on the highway, because the laws of physics for trains are the same as those for cars - you can only stop a moving vehicle so fast in a safe manner without loosing control or causing harm to its occupants.
Skytrain equipment is professionally maintained to very high safety and reliability standards and operates in a protected right of way in which risks from random events are minimized, yet every train is required to be separated from every other train by at least the safe stopping distance. Yet we expect mass produced privately owned vehicles operating in a wide-open threat environment to run around at high speeds with mere feet separating them? There seems to be a big reality gap in there somewhere...