A tutorial on one good method for switching classification yards
There are many ways to work a model (or prototype) yard. One of the least
efficient ways is to "Cherry Pick". This involves looking over the whole yard, selecting the dozen or so cars one needs from
all the tracks, then pulling each track individually in turn to pick out just those cars while putting back the rest.
Prototype flat (non-hump) classification yards are not typically operated
in this fashion. Instead, tracks are pulled as few times as possible to increase efficiency.
This is not the only way, of course, but it works well even if there are
only one or two tracks clear. To illustrate this idea, we'll go through an example of one way to switch a flat classification
yard in the model. This example is very simplified, focusing only on classifying what exists in the yard at the start of the
session. In fact, of course, new cars would be added as trains set-out blocks or terminated in the yard.
The yard configuration itself is also very simple: a single-ended flat yard
with no arrival/departure tracks. Cars are needed in this order: Amboy Local; Eastbounds; Baker-Cadiz Local; Westbounds. Cars
for the two locals must be classified before leaving the yard, but there is no specific station order required within the
East or West blocks. Placing the cars for each local involves placing them in order from 1 to 3 reading from left to right.
For the Backer-Cadiz local, cars should be placed B 1-3, then C 1-3, again reading left to right. Also assume that our switcher
can only pull about 8 or 9 cars at a time (about the capacity of each track plus one or two cars). We'll also assume that
we can't "kick" cars but will need to move them all the way to their final location with the switcher.
"... tracks are pulled as few times as possible
to increase efficiency."
Here's the situation when the yard crew comes on duty (Figure 1). There are five groups of cars in the yard: eastbound
cars for destinations off the layout (long Easts, blue cars labeled "E"); long Wests (gold cars labeled "W"; cars to be blocked
for the local to the town of Amboy (green, labeled "A 1-3" for their blocking order), cars to be blocked for the local which
serves the two towns of Baker and Cadiz (red, labeled "B" or "C" and numbered for their blocking order), and cars that won't
be needed until tomorrow (the next session) or later (brown, labeled "T").
Obviously, this yard is a little too full, but since we won't be getting any inbounds that situation will improve as
we start to make our moves. What's the best first move? There may not be one "right" answer. My experience of watching many
different operators of varying degrees of experience switch the same model yard suggests that experience and exposure play
some role in how operators approach the task, but there is probably also some component of individual differences in the way
we each see and categorize the world. This has been true even for different prototype railroaders operating on that same modeled
yard: each approached the job differently based on experience and personal perception.
(click any yard image for a larger view in a new window)
"...even different prototype railroaders operating
on [the] same modeled yard ... approached the job differently ..."
One less-efficient way would be to cherry-pick the tracks to start building
the Amboy train. I have watched novice operators do just this in similar situations and they do a good job of getting the
first train done. Unfortunately, because they have made no progress on the second or third block while switching the first,
those trains or blocks are not ready when the call time comes and the session can begin to bog down. Certainly, the stress
level in the yard increases! Cherry-pickers might be tempted by that A3 car sitting at the end of track 5 and start building
the Amboy train on the open track 2. It should be noted that cherry-picking does work -- for the first train or block.
The result of a strict cherry-picker working our yard can be seen in figure 2. After many back and forth moves pulling from
three tracks, Amboy's ready. But the rest of the yard is still a "dog's breakfast". (Figure 2)
The alternative approach seeks to work each track as few times as necessary
while still keeping in mind the order in which cars are needed (Amboys, Easts, Baker-Cadiz cars, and finally Wests). Tracks
5 and 6 are pretty rich in Amboys and Easts, so those are tempting first moves. My personal preference, though, would be to
grab ... track 3!
Yes, there are multiple ways to approach this and other first moves could also work well. But
my reasoning is that I'd like to have more tracks open to use for classifying cars. Track 3 has a fairly short cut of cars
and there is an East right on the end that will be next to the engine so I can hang on to it for later moves. And I'll shove
the rest of the cars from 3 down on track 1. It's the longest, so it makes a good "slop" or "for now" track. And there are
already those two "Tomorrow" cars at the end that I may not need to touch again if I am lucky. Because we can't kick cars
I'll take this opportunity to push the cut to the end of the track since I know I'll need the space later.
So after my first quick move or two, I've cleared an extra track and I'm
holding on to that East car (Figure 3). Now I'd probably latch on to track 5. It's got the highest percentage of Amboys and
Easts. (Track 4 is another good candidate since it's adjacent to the open tracks, but I've got other plans for that one).
The other nice thing about track 5 is that the Amboys on that track are already in station order -- always something to exploit