Re: Modeling freight car distribution.

tim gilbert <tgilbert@...>

Bruce Smith wrote:


At least I made you happy with the NH car <VBG>. Of course, the bottom
line is that you never know what will show up in the mix of cars out on
the road. The "gap" between the total and the planned number of cars
allows for some additional cars of interest (Like that Rutland box car,
or an A&S or...). Of course, I'm working on a detailed listing for
flats, gons, reefers and stock cars. I do have a Rutland stock car to
build too!

Be careful of trying to extrapolate the ownership distribution of
boxcars into other car types. With the exception maybe of general
service flat cars, the other car types on line do not correlate that
well with the ownership distribution. The principal reason is the
differences in the ratio of empty car miles to loaded car miles of each
car type per the following table:

1948/49 1956/56 1968 1972
Boxcars 0.32 0.36 0.55 0.72
Gondolas 0.67 0.79 0.89
Hoppers 0.85 0.90 0.90
Cov. Hops. 1.13 1.04 1.02
Hoppers & Gons 0.75 0.81
Reefers 0.63 0.72 0.69 0.77
Tank Cars 1.00 1.04 1.08 0.96
Flat Cars 0.55 0.67 0.80 0.96
TOFC 0.32 0.47
Total 0.54 0.58

The lower the ratio, the more apt that the car will deviate from an "out
loaded & back empty" scenario.

Tim Gilbert

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