Outbound operation, historically, has always been faster than
inbound operation. Once the train leaves Embarcadero, it runs
quickly, loads quickly, and is out of the way, and its place is
quickly filled by the next train, etc.
Historically inbound service has been slower than outbound because
inbound trains were hitting the turnback congestion at Embarcadero and
had nowhere else to go. Outbound services see "only" dwell time and
breakdown delays, and so of course they're faster.
This doesn't explain how things queue up now that MMT is open.
The answer to that, of course, is that outbound dwell times are
longest at Embarcadero. Otherwise, of course, equally large queues of
trains would consistently bunch up at other points in the subway. So
cutting the effective dwell time at Embarcadero, by overlapping the
boarding of two or more trains using two or more platform locations,
can hope to increase overall system throughput and not just
immediately move the bottleneck to some downstream location.
The queue of trains behind it are empty (with the exception of the
ones coming from MMX), and it doesn't matter as much to have them
wait.
Oh yes it does! It means that those trains are Not In Service, which is
a bad thing if you're a Muni customer trying to get somewhere.
Having a train use the inbound platform to go outbound will always
hold up the trains behind it, and it will confuse an already
frustrated throng of people waiting at Embarcadero. Isn't a queue
of empty trains waiting to load better than a queue of inbound
trains, all with passengers aboard, stuck between stations? I
would think so.
Again, you're conflating the only operation pattern of pre-MMT Metro,
in which _all_ train paths were serialized over the Embarcadero
scissors, with what I'm proposing, which is that that scissors be used
precisely when there is no contention and so no significant delay
would be induced. It is easy for a computer system or a human looking
at the spacing of the string of approaching trains to determine when
this is so.
Passengers can easily understand annunciation (signs, spoken, vehicle
destinations) of which platform is the next outbound train. Even in
the intellectually slack environs of San Francisco they somehow
managed this advanced cognitive feat for fifteen years.
And once again, for the last time, a queue of empty trains is a queue
of useless trains, just as a queue of full but stationary trains is.
Fortunately, these aren't the only choices.
[...]
Why are you so worried about this "4+ minute non-revenue-service penalty"?
Because San Francisco's Muni is literally falling apart, and lack of
vehicles and lack of operators has always been a huge contributor to
that problem.
Because 4 minutes is 5% of an 80 minute round-trip, which means that
an extra four minutes per trip means the effective loss of 5% of the
vehicles and 5% of the operators in the fleet. That means 97 3.5
million dollar vehicles are required to do the work of 92. And so on.
That means that $17 million worth of extremely scarce equipment is
effectively sitting around depreciating instead of providing revenue
service.
It's basic arithmetic. Vehicles and operators should be serving
actual customers to the maximal feasible extent, not cooling their
heels in some salubrious underground facility.
Throughput, particularly at rush hour, is the name of the game.
Bums on seats, and seats moving along the line.
I've nothing against layovers or schedule recovery or operator rest
breaks; I just don't think that Embarcadero at peak is the time or
place.
In Boston, every train arriving a terminal discharges its
passengers, goes into a non-revenue layover point, and the
personnel prepare for the next revenue trip by changing ends.
Warning: choo choo nerd talk! Actually, at Park Street and Government
Center (the most Embarcadero-analogous places where most services on
the Muni-metro-analogous Green Line turn back) trains reverse by
running around a balloon loop and immediately reappearing on the
outbound platforms. (Non-revenue balloons are also used at some outer
terminals.) The high-platform, more-subway-like Red and Orange Line
trains reverse at the platforms of their two-track, stub-end terminals
rather than using the tail tracks. Only at the Wonderland end of the
Blue Line do trains regularly reverse in the tail tracks (the Bowdoin
end runs around the to-be-closed non-revenue balloon.)
I've said my piece on this. I don't think it's of sufficiently wide
interest to continue inflicting on a general readership list, so I'll
say no more for the nonce.