Looking at german Stadtbahn systems (trams with a evtensive dedicated RoW & central tunnels, but still a lot of street-running), they archieve headways down to 2 minutes, e.g. in on of the central sections of the Stuttgart Stadtbahn.
That should probably be doable on some american light rail systems, with signal priority and avoiding street running on roads with a lot of traffic congestion.
Re:How Many Tracks Do Train Stations Need?
by dredmorbius on Friday June 17, 2022 @05:26AM
(#31775896)
Speed may be a factor, as stopping distance (and time) increase with speed. Low-speed LRV can achieve shorter headways.
BART operates up to 80 mph (128 kph), though I'm not sure it hits those speeds within San Francisco.
Re:How Many Tracks Do Train Stations Need?
by iggldiggl on Friday June 17, 2022 @03:49PM
(#31783364)
For urban railways, stations are usually the capacity-limiting factor, so the top speed doesn't really enter into it, and besides
> though I'm not sure it hits those speeds within San Francisco.
due to the shorter station spacing I'd assume that, too.
As for the stations, the limiting factor in turn consists of the sum of dwell time (wheel stop to wheel start) and platform reoccupation time (governed by the signalling system).
Re:How Many Tracks Do Train Stations Need?
by dredmorbius on Saturday June 18, 2022 @12:12AM
(#31787207)
That sounds about right.
For light-rail transit, shared routes (LRV + automobiles) and traffic signals mean that arrivals are not predictable. Where shared-roadway and dedicated-route segments exist (say, with San Francisco's Muni Metro), hold times must be built in for the dedicated-route travel segments. Train arrivals are highly unpredictable. A level below Muni, on Bart, rush-hour headways through the San Francisco subway are 4 minutes. That's close to the theoretical maximum Alon gives of two minutes.
For conventional heavy rail, boarding / debarking delays, equipment failures, medical emergencies, police activity, level-grade collisions, and other factors, may all lead to service delays.
Signalling matters mostly in that it both doesn't introduce new delays into the system, and that it can compensate for delays originating elsewhere.
Reliability overall, as discussed in the article, is largely based around signalling to manage flows.