STAGING TRAIN LENGTH (Cars):
Write this stat as three values sep-
arated by slashes – longest/average/shortest. Longest is the length
of your longest staging track in cars. Average is the length an aver-
age staging track in cars, computed as:
staging track / number of
staging tracks.
Shortest is the length of your shortest staging track
in cars.
Ideally, staging train lengths should more or less equal the corre-
sponding passing train lengths. Significantly smaller staging train
lengths mean extra switching will be involved in getting a “full
length” train into or out of staging. Larger staging train lengths
mean full length opposing trains from staging will clog the main.
The longer of passing or staging train length should rule in deter-
mining typical long train length. The shorter of passing or staging
train lengths should rule in determining typical average and short
train lengths.
You may notice that staging tracks and passing tracks appear
somewhat interchangeable in these formulas. This either/or use
of staging and passing sidings reflects an operating session real-
ity (one that was actually exploited by Tony Koester on his AM,
by the way) where the layout’s staging can be viewed as “virtual
passing sidings”.
“Ideally, staging train lengths
should more or less equal
the corresponding passing
train lengths.”
Layout design assessment - 7
For example, the dispatcher could set up a “meet” between oppos-
ing trains to occur offstage. To do such a “meet,” one train exits the
layout into staging, after which a different train enters the layout
– as if a meet had just taken place in an offstage passing siding. If
some of the passing sidings on the layout are rather short, this can
be a useful technique for arranging meets between longer trains.
OPERATING POTENTIAL
From the basic stats, we can quickly estimate the layout’s operat-
ing potential. Way back in June 1968,
Model Railroader
published
“Layout plans by formula”, written by Dr. Roy F. Dohn. Dr. Dohn
described how to estimate the operating potential of a track plan
using some clever formulas he developed by working backwards
from actual operating model railroads.
Using his formulas as a starting point, I have developed an updated
set of formulas.
MAXIMUMNUMBER OF CARS:
A layout can only hold so many
cars before it gets difficult to move cars because the destinations
are at capacity. This upper limit seems to be around 80% of the
total capacity for stationary cars, so we can compute this as:
80%
of (storage + staging + passing/2)
.
To allow for more cars on the layout, increase the amount of stor-
age and/or staging track, or to a lesser degree, add some passing
track capacity. Generally, passing trackage is not intended to be
used as permanent storage, so to indicate that some passing siding
capacity could be used as short-term storage, a factor of one half is
suggested in the formula.
MAX-TO-MAIN:
We can take the max number of cars and compare
it to the total mainline car capacity to get a sense of howmuch
mainline running a layout has versus howmuch non-mainline
MRH-Oct 2014
