----- Original Message -----
From: Dave Nelson
To: STMFC@...
Sent: Monday, May 04, 2009 3:27 PM
Subject: RE: [STMFC] "A" Railroads Base Fleet





Charlie Vlk wrote:

> Wheel reports, photos of entire trains, or overall photos of yards
> for the road you are modeling or similar ones in the region you are
> interested in, in your era, would be more instructive than a
> mathematical model.... if you can find such documents. Charlie Vlk

And so we did.

Charlie, when I developed the hypothesis I did not have any wheel reports
but with the understanding that a good set of such documents would either
confirm or refute the whole idea, I went out and purchased as many as I
could. About that time I met Tim Muir and he too was looking for wheel
reports, pretty much for the same reason, and from that point on we
collaborated on our analysis. Tim took a much more vocal role in promoting
the idea than I did and on his own he explored and discussed the possibility
that the hypothesis could also be applied to ordinary flat cars.

Eventually we collected quite a few wheel reports. I have about 30 for the
Southern, and individual books from the NYC, UP, SN, and something else I
don't recall right now, and a Yard Jumbo from the W≤ Tim had his own set,
which I know included another some from the Southern as well as the UP...
the others don't come to mind right now.

The wheel reports did, IMO, confirm the basic hypothesis and allowed us to
further specify when it applied: Post WWII, on mainline trunk routes,
excluding home road boxcars, the percentage of boxcars marked for foreign
roads will closely match the percentages of boxcars contributed to the US
fleet by each railroad. By boxcar, I mean one that can be put into general
purpose use. The wheel reports do show a bit of a bias towards nearby
connections, but here I believe the sample size of locations that we have is
too small to make a good hypothesis on that point. Further, as almost all
railroads contributed less than 5% of the national fleet (most less than
1.5%), even a large bias towards local connections would compute to a very
small number per 100 foreign road boxcars.

Last, the hypothesis makes no predicition on what one might observe in
individual trains.

As to the available alternatives: IMO yard photos can be useful but the
number of home road cars is usually wildly over-represented as compared to
what the railroads reported to the ICC. Photos of whole trains are one data
point, the same as a wheel report, but as single trains are usually blocks
from connections (or destinations), their makeup is very likely *not*
representative of what you'd record after observing a set of freight trains
on the same route in the same period of time. They also have the same
problem as yard shots -- it's just one point in time. Based on the wheel
reports, it's clear that things vary all of the time. A sample from one
moment, as what a photo shows, is simply not going to be fully
representative.

So in the end, it is my opinion that wheel reports do provide the sample
that's useful, and they do confirm the mathematical model -- not precisely
-- but very, very well.

Dave Nelson






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