Thursday, June 10, 2010

Scheduling

I am trying to come to grips with the degree of mental retardation that I suffer.

I've looked at and pondered the reason for "timed transfer" on Cal-train schedules for the past week as I ride the train to work.

But I just couldn't figure out why it is arranged the way it is. Below is a picture of the timed transfer between 207 and 211


Basically, it is a slow ride that stops at every station on the 207 to the transfer stations, after which you can transfer to the other train (the 211) and it stops every station from there onward.

So if you had to get from a non-major station in the upper segment, to a non-major station in the lower segment, you have to ride slow all the way.

Would we not accomplish the same with two trains? a slow train that stops every stop, and a faster train that met it half way? that way, if I travel to a minor station in the lower half, I take the faster train to the middle point and then transfer to slower train. If I travel from a minor station in the top half to a major station below, then, I get on the slow train, and meet the fast train half way and ride that to my destination that is a major train in the lower half?

So, to draw it out, make 207' stop every where, and let's say it still arrived in the green transfer stations at 6:39. Let's make the baby bullet 309' a limited express that stopped at all stations 309 and 211 stops at in the upper half, and arrive at green transfer station at 6:39. In the lower half, 207' still makes every stop, and 309' makes all stops that 309 and 207 makes in the lower half.

Then, every one in the minor station above can get to the transfer point, and arrive at at least one of the major stations below. Every one at a major station above, can still get to a minor lower station.

This way, what Cal-train can do is run longer trains (8 instead of 4 or 5) and save some diesel. Surely, two trains 8 sections each uses less diesel than 3 trains 5 each.


I even searched google for the answer, but I just don't understand it. If we insist on two green transfer stations, it could provide shuttle service.... (since in our scheme we only have one transfer station where as in previous scheme there were two)

1 comment:

  1. Caltrain being a train service that is actually on time most of the time can follow the proposed scheme. The only disadvantage it has is that it requires the two train to be at the station simultaneously. This means if one train was to be late by 3 minutes, the other train will sit there for 3 minutes and wait for it.

    This is more difficult to arrange than the timed transfer they implement which only requires that one train be ahead of the other. This constraint is easy to satisfy in this situation because they run on the same track.

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