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Re: A Purpose For Frt Car Distribution Studies

Malcolm Laughlin <mlaughlinnyc@...>
 

It would appear that we are headed down the road of confusing average
and mean. Which are totally different. Given 10,000 freight cars past a given point, the average will most likely mimic the national fleet based on Tim and Dave's data. However, the mean may be skewed in one direction or the other significantly.
====================

Tim's data doesn't say that. He has the percentages of system and foreign ownerships on line and off line. It's a big leap of faith to extrapolate that distribution of individual ownerships.


Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478


Re: A Purpose For Frt Car Distribution Studies. Was: Re: Re

Malcolm Laughlin <mlaughlinnyc@...>
 

Steve Lucas writes:

"Tony--

After reading this thread for some time, I have to agree with your basic premise. Most major through transcon routes such as the UP in Wyoming would very likely have over a given period, percentages of each road's boxcars in keeping with the national averages. The law of averages supports this."
------------

I say that statement is dead wrong.
================


Well...perhaps someone's law of averages supports it but the data does not. Can you explain that?
--------------------------------------

The law of averages, or the law of large numbers, works only for homogeneous data sets. The national box car fleet did not meet that qualification. It could be reasonably be said to apply to the percentages of NYC, PRR and B&O amrks on the UP, but not to the number of thsoe marks releative to UP direct connsections.



Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478


Re: Freight car distribution

Malcolm Laughlin <mlaughlinnyc@...>
 

Posted by: "John Stokes" >This is the other factor in this essentially impossible and largely meaningless exercise in trying to figure out how many cars of each type would typically be seen on a train in the time period selected and then extrapolate that information to one's model railroad.

Agreed. The whole exercise is meaningless because it's all predicated on the equal percentage of all ownerships on all railraods, a totally unwarranted assumption. If I looked at a model railroad situated in California and saw percentages of FEC, CGA, B&M, RDG, RF&P cars that were not a lot less than SP, WP, SP&S and other westen marks percentages of the national fleet, I would know he's not really modeling the region, but wants to give eastern cars equl weight.


Reality is not the same as a computer simulation under the rather limited and primitive conditions we are working in here. It doesn't take a long time looking at photos, for example, of Northern Pacific or Great Northern freight trains and yards to see that at least on the days the pictures were taken, home road equipment often dominated, but the stats say otherwise. Go figure. Glad you are having fun with all this, Mike.
Using computers, you can get all sorts of detailed calculations based on data and assumptions that are wrong. Unless you are sure of the assumptions, those calculations are useless. I say this as one who believes in computer models and has used them at various time since 1966. But it's a total waste if the initial data assumptions are invalid, which I say is the case for all of those Excel calculations.




Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478


Re: DTI trucks

Rich <SUVCWORR@...>
 

--- In STMFC@yahoogroups.com, Tim O'Connor <timboconnor@...> wrote:

Brian

You may not be aware but the earliest version of those trucks
I've seen were cast in 1934 by ASF, while the DT&I cars were
built (with different castings from unknown foundry) in 1949.
So someone had the coil-leaf-coil trucks before DT&I. (Or they
were applied to some other DT&I cars.)
PRR truck class 2D-F10 tracing e-94261 issued 1932. These were used
under FM class flat cars, X29 and X35 boxcars.

http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=2d-
f10.gif&sel=ftk&sz=sm&fr=

Rich Orr


Re: Box car counts by RR - NMRA Charles collection

boyds1949 <E27ca@...>
 

I don't think we can draw too many conclusions on car distrubution
based on the list of cars in the Charles Collection other than to
marvel at the variety of cars which stopped in Harrisburg. The
selection of cars to photograph was at the descretion of the
photographer. Cars in accessable areas or cars which were of
interest to the photographer may have been more likely to have been
photographed so the list may not be a representative sample.

The UP and Southern conductor's books list every car that the
conductor encountered in their trains and should be more likely to be
representative samples for the territories covered.

John King



--- In STMFC@yahoogroups.com, Malcolm Laughlin <mlaughlinnyc@...>
wrote:

I believe that the random variables in this situation are the
boxcar
counts for each railroad.
================

The box car ownership counts themselves are highly biased. A
significant percentage of the box cars was our of service. For
example, obsolete cars used only in the harvest season for grain
loading to a very limited number of destination cities, cars aiting
for rebuilding, cars designated for shop programs for special
equipment, etc., etc. Depending on the railroad those could account
for anywhere from five to 20 percent of the box cars.

There are other biases in the live cars. Like 50' DD or WD cars
for lumber loading, cars with six foot doors useful for grain but
likely to be rejected by many shippers. There were os many XM box
cars with dimensional characteristics that would keep them from being
randomly distributed.


Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478



Re: Battleship Gons trucks

Jared Harper <harper-brown@...>
 

--- In STMFC@yahoogroups.com, " Westerfield" <westerfield@...> wrote:

Al - C&O battleships can reasonably be modelled from Buckeyes. N&W
early battleships used Pilchers which are available from Bethlehem Car
Works. The Lewis trucks are unlike anything on the market but are
simple enough to scratch build. - Al Westerfield


The Lewis trucks were offered separately in brass by NWSL some years
ago. You may find some if you look.
Jared Harper
Athens, GA


Re: Box car counts by RR - NMRA Charles collection

Malcolm Laughlin <mlaughlinnyc@...>
 

I believe that the random variables in this situation are the boxcar
counts for each railroad.
================

The box car ownership counts themselves are highly biased. A significant percentage of the box cars was our of service. For example, obsolete cars used only in the harvest season for grain loading to a very limited number of destination cities, cars aiting for rebuilding, cars designated for shop programs for special equipment, etc., etc. Depending on the railroad those could account for anywhere from five to 20 percent of the box cars.

There are other biases in the live cars. Like 50' DD or WD cars for lumber loading, cars with six foot doors useful for grain but likely to be rejected by many shippers. There were os many XM box cars with dimensional characteristics that would keep them from being randomly distributed.


Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478


Re: A Purpose For Frt Car Distribution Studies

Rich <SUVCWORR@...>
 


-Does- average always mean the same thing? I learned (correctly, I
hope) that "average" could be one of three things; mean, median or
mode. Usually when folks - those unencumbered by formal education -
say "average" they actually mean "arithmetic mean."

Gene Green
OitwTtoEP
Average amd median are the same thing. total events/number of
observations eg. you observe 100 trains and those trains have 273 ATSF
cars in them. The average number of ATSF cars in a train is 2.73

Mean is that value where 50% of the observations are above or below it

Mode it the value that occurs most frequently.

eg. you observe 10 trains with the following number of PRR cars

3, 0, 3, 1l, 0, 0, 1, 8, 1, 13 total number of cars = 40 average =
4.0 cars per train mean = 2 mode = 0

Rich orr


Re: Freight car distribution

Mike Brock <brockm@...>
 

Tim O'Conner says:

"Mike Brock wrote

My point exactly. The theory doesn't seem to apply to the
Overland Route for SP, CB&Q, C&NW, and Milw...
Actually, it applies exactly to the Overland Route. Your
samples are just too few to be statistically meaningful."

My point again...as I've said from the first. But it IS the data we have. We just don't have enough data to make any definite judgements. The Nelson/Gilbert theory is interesting and useful...as I've said also...but IMO I wouldn't use it to predict or project accurate frt car populations as it exists today. Meaning that, IMO, it needs a bit of adjustment for closely associated RRs...like the Overland Route among others.

"It's not even one day's worth of trains on the UP."

In 1949 it is slightly more than one day's trains.

"The
data do not support ANYONE's theory. In the absence of
data, logic must prevail."

Now I know you're kidding <G>.

"Give me a logical explanation
for your consists, please! All you've said basically is
that Tim was wrong, based on a minute sliver of data. If
you have a better theory, I'm all ears."

That's simple. 1. Fraley loved SP box cars. He liked to run on trains filled with them when possible. He even rode in them sometimes. 2.WP, ATSF, GN, and NP CEO's hated the CEO of SP [ he always beat them at their poker games in Vegas...among other things ] so they wouldn't take his box cars. The UP CEO was never sober enough to gamble. 3. There was a photographer in Omaha...General Malcom B. Malcolm [ also know for having one of 25 gold Big Boys made in Burma in '43 [ the other 24 were sunk in the Yamato Maru incident ]. Malcolm loved to shoot SP box cars so he bribed the SP CEO's secretary to make sure SP box cars went through Omaha.

Tim wasn't wrong. The theory simply fails for the data that we have for the Overland Route. As you'll note in one of his messages to me...that I reprinted...he noticed that as well as I did. A lot of theories break down and have to be adjusted when they fail the test of data. In this case we have no way of knowing if the theory is failing because of the data or the lack of data.

Mike Brock


Re: A Purpose For Frt Car Distribution Studies

Malcolm Laughlin <mlaughlinnyc@...>
 

Posted by: "Gene Green" bierglaeser@yahoo.com bierglaeser Sun Aug 17, 2008 8:07 am (PDT) --- In STMFC@yahoogroups. com, Anthony Thompson <thompson@.. .> wrote:

An average always means the same thing, Malcolm, though in a skewed distribution it will not lie at the same location as the most frequent data, which lay persons usually assume the average to be (and which it is in a symmetrical distribution) . But I have no idea what a "true average" is.
I'm well aware of the mean-mode-median thing, but to me "average" has always meant the sum of the observations divided by the count. But in the case of the distribution of freight cars 50 years ago, it really doesn't matter, we can't get enough data to make distinctions of that sort. I'd be amazed if anyone could find a good number for the percentage cars on-line by ownership for any day, week, month or year in the 50's or 60's. In the 50's the data couldn't have existed. If certain computer tapes on the Southern or NYC (and a very few others) from the mid-60's were still around we could do a count. There really was no reason for a railroad to do the count because it had no value for car management.

I'll repeat what I said yesterday about the value of an average number in this environment. Somoene said an average was a good start point. I agree in the sense that it's better than no number and beginning with an estimate of zero or infinity.

As for the percentage of cars by ownership on any one railroad, I think it's absurd to suggest that it might be the national average ownership.

I'm willing to wager that there was never a day when the distribution of cars across a railroad was ever within 20 percent of that average for more than 50 percent of the ownerships on line, excluding roads and ownerships too small for significance. Tim's calculation of that statistic, or just the fact that it can be calculated, does not make the result meaningful in the real world.

Taking a few consists (1000 is few in this context) and finding that they come close to the estimate is very shgaky statiatically. In many fields of research, using selected historical data to verify statistics is frowned upon because it is very subject to selection bias. That is when the researcher finds a correlation and announces it. But what really should be done is to make a good number if independent estimates using other data sets of the same kind to see if the results are reproducible. In this case that would require taking some number, like 10, other sets of unrelated consists on other railroads in different sections of the countryand comparing the results.



Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478


Re: Freight car distribution

gn3397 <heninger@...>
 

--- In STMFC@yahoogroups.com, John Stokes <ggstokes@...> wrote:

Again, the best and perhaps only lesson is to try to avoid the "iconic" cars when they were
actually few in number, and balance your cars, with a good dose of home road cars,
depending on what the history of your prototype was at any given time, when they had or
didn't have a large fleet or kept it close to home, as in grain shipment time or on
dedicated mineral runs.

Reality is not the same as a computer simulation under the rather limited and primitive
conditions we are working in here.

It doesn't take a long time looking at photos, for example, of Northern Pacific or Great
Northern freight trains and yards to see that at least on the days the pictures were taken,
home road equipment often dominated, but the stats say otherwise. Go figure. Glad you
are having fun with all this, Mike.

John Stokes
Bellevue, WA
Mr. Stokes,
Actually, if you are modeling GN or NP immediately postwar, you will only want about
15-20% home road boxcars if you are modeling the grain rush in the fall. One of the more
fascinating ads that I found in my local paper's archive back in ND (which I stupidly didn't
copy) was a half page ad the GN placed in September 1946 explaining the lack of cars. If I
recall, the GN stated it only had about 3000 of its own boxcars online, of a fleet of approx
22,000 at the time. GN (and I am sure Soo and NP) were routinely excoriated by local
farmers and elevator operators because of a shortage of suitable boxcars for transporting
wheat to market.

I have corresponded with a couple of GN employees from this time period, one a
trainmaster, and one a rural station agent, and they both stated that car supply was a
constant headache. GN couldn't get its cars back online fast enough, despite putting out
warrants a few months ahead of time. The Eastern roads would also usually send their
worn out cars to the GN, which often were unsuitable for grain loading. Usually the linings
weren't grain tight, so loss in transit was an issue. GN maintained the linings of its cars
pretty well, because grain was the most important single commodity it carried. The
trainmaster I spoke to related the time he sent a solid 100 car train of mostly eastern
boxcars up a branch in eastern Montana, with rolls of heavy paper and coopering
materials supplied by the GN, and the next day 97 came back empty because they had
been refused by the local elevators!

I think another important point, which Mr. Gilbert repeatedly emphasized, was the state
of the US economy. All the 1930s era photos I have seen of GN stations and branches
show a preponderance (100% in some instances) of GN boxcars, no doubt because of the
poor economy lowering demand for cars, thereby allowing GN to keep its cars online.
Obviously, the situation was different postwar.

Anyway, this is an interesting discussion. I wish I had some conductors books or wheel
reports from some of the GN branches I am interested in to get a better feel for the car
distribution, but I have never come across any. I don't know that my layout will ever
accurately represent the actual percentages of boxcars that operated on the particular GN
branchline I am modeling, but I am shooting for 20% home road boxcars, and the other
80% will be distributed among the national percentages. If anyone ever finds data to
refute that, I would love to see it.

Sincerely,
Robert D. Heninger
Iowa City, IA


Re: A Purpose For Frt Car Distribution Studies

Rich <SUVCWORR@...>
 

--- In STMFC@yahoogroups.com, Anthony Thompson <thompson@...> wrote:

Malcolm Laughlin wrote:
I'm OK with the average as the core datum, but recognizing that
the
average in the car distribution case may be at one side of a
skewed
distribution orm otherwise not a true average. Any average is
better
than zero or infinity as the starting point.
An average always means the same thing, Malcolm, though in
a
skewed distribution it will not lie at the same location as the
most
frequent data, which lay persons usually assume the average to be
(and
which it is in a symmetrical distribution). But I have no idea what
a
"true average" is.
It would appear that we are headed down the road of confusing average
and mean. Which are totally different. Given 10,000 freight cars
past a given point, the average will most likely mimic the national
fleet based on Tim and Dave's data. However, the mean may be skewed
in one direction or the other significantly.

Rich Orr

Rich Orr


Re: Freight car distribution

Mike Brock <brockm@...>
 

John Stokes writes:

"This is the other factor in this essentially impossible and largely meaningless exercise in trying to figure out how many cars of each type would typically be seen on a train in the time period selected and then extrapolate that information to one's model railroad. Who has 1000 + cars? Who has the full mix of car types within box car classes alone and who has a layout on which to run full length freight trains? Not very many of us at all."

Well...certainly not me. UP trains in my time period weere about 82 cars in length. Much of this was based on tonnage ratings. The line in question...between Laramie and Green River has...I believe...a max of 0.82 grade and UP generally liked to run relatively fast frt trains. Layout compression drops frt train lengths for me by at least 50%. 3 of 35 UP frt trains that we know of had 27-36 SP box cars in their consist. Assuming an 82 car length...I ain't gonna look it up...means the 3 trains had from 32% to 43% SP box cars. If I were to run a 40 car frt it could contain as many as 17 SP box cars. Well. Guess what. I don't have 17 SP box cars.

"Again, the best and perhaps only lesson is to try to avoid the "iconic" cars when they were actually few in number, and balance your cars, with a good dose of home road cars, depending on what the history of your prototype was at any given time, when they had or didn't have a large fleet or kept it close to home, as in grain shipment time or on dedicated mineral runs."

I agree. I will admit...as I have said...that it is sorta interesting to see a photo of cars where they "shouldn't be".

"Go figure. Glad you are having fun with all this, Mike."

Well, John, it's like this. Why else would I wade through this <G>.

Mike Brock


Re: diversions.

Malcolm Laughlin <mlaughlinnyc@...>
 

Posted by: "Bill McCoy" Diversions could be filed by the beneficial owner of the car's lading
as shown on the Bill of Lading and reflected on the Waybill that
accompanied the car. Up to 3 diversions could be made on a car IIRC.

============

Thanks for that input Bill. I'm glad to know there is someone on this list who saw the diversions at the working level. My input was from a more thoretical management level, but looks like we agree on the basic game/


Malcolm Laughlin, Editor 617-489-4383
New England Rail Shipper Directories
19 Holden Road, Belmont, MA 02478


A Purpose For Frt Car Distribution Studies. Was: Re: Re

Steve Lucas <stevelucas3@...>
 

Wrong phrase, from an admitted statistical neophyte. I should have
referred to the "law of large numbers".

http://en.wikipedia.org/wiki/Law_of_large_numbers

Steve Lucas.

.--- In STMFC@yahoogroups.com, "Mike Brock" <brockm@...> wrote:

Steve Lucas writes:

"Tony--

After reading this thread for some time, I have to agree with your
basic premise. Most major through transcon routes such as the UP in
Wyoming would very likely have over a given period, percentages of
each road's boxcars in keeping with the national averages. The law
of averages supports this."

Well...perhaps someone's law of averages supports it but the data
does not.
Can you explain that?

Mike Brock


Re: Freight car distribution

Tim O'Connor
 

Mike Brock wrote

My point exactly. The theory doesn't seem to apply to the
Overland Route for SP, CB&Q, C&NW, and Milw...
Actually, it applies exactly to the Overland Route. Your
samples are just too few to be statistically meaningful.
It's not even one day's worth of trains on the UP. The
data do not support ANYONE's theory. In the absence of
data, logic must prevail. Give me a logical explanation
for your consists, please! All you've said basically is
that Tim was wrong, based on a minute sliver of data. If
you have a better theory, I'm all ears.

Tim O'Connor


Re: Freight car distribution

Tim O'Connor
 

We've been down this road too -- most people take photos of
stuff they happen to like, or that catches their interest.
Almost no one took photos (and expended film) in order to
document "typical" stuff. Ergo: photos are not admissible
as evidence of anything other than what is depicted in them.

By the way, being an GN and NP fan, I've seen many photos
on each railroad where virtually no home road cars can be
seen. Including the infamous NP Montana branch line train
with a bunch of PRR empties headed to a grain elevator...

Tim O'

It doesn't take a long time looking at photos, for example, of Northern Pacific or Great Northern freight trains and yards to see that at least on the days the pictures were taken, home road equipment often dominated, but the stats say otherwise. Go figure. Glad you are having fun with all this, Mike.

John Stokes
Bellevue, WA


Re: Freight car distribution

Mike Brock <brockm@...>
 

Tim O'Connor writes:

"Mike, he ran 100,000 iterations of a 40 car box car train, composed
of cars chosen randomly from every possible prototype."

OK.

"The National
% is obvious,"

OK. 3.9% for SP in 1949.

"and then he finds the AVERAGE % found for that railroad
in the random consists. What is not obvious about this?"

Nothing. What's the value...IOW, so what?

I tallied the maximum number of cars for each railroad over all the
iterations. In a 40 boxcar train, the average number of cars would be
40 times the national percentage shown in the above table."
Why do you say that?
"Because he described it obscurely. He simply kept track of the largest
number of cars seen for each reporting mark in the 100,000 trains. Is
this not also obvious?

Well...actually that's not so at all. The correct number is 4. 136/34
If you use real...rather than theoretical data.
Real what? 136 box cars?"

Yep.

"Larry's example was PURELY theoretical, and he made an excellent point.
I guess some people just don't get it."

What's there to get?

We know that there were 4 of 34 trains...11.76%...of the trains with
far more than 9 SP bx cars.
Mike, you are having trouble grasping the idea. Larry has presented
100,00 theoretical trains, of fixed length, of random composition.
You persist with your miniscule sample of 34 actual trains of
varying length and composition of different sorts of cars (not just
box cars)."

Yep.

The 1953 data shows the "infamous" train with 36 or more SP box cars
[not T&NO ].
Yes, but I will argue that the Overland Route for the UP and SP was
a 'home road extension' in that each road was highly dependent on the
other for traffic. Therefore we can discount the presence of SP as
well as UP cars in all trains over Sherman Hill, for the purposes of
this discussion. This is exactly the "skew" that each layout has to
consider."

My point exactly. The theory doesn't seem to apply to the Overland Route for SP, CB&Q, C&NW, and Milw...although SP is the most significant violator. Other RRs might have similar situations...i.e, SP and SSW...ATSF and...well...ATSF. NP and GN with respect to CB&Q might also apply. Others might be MP and D&RGW and WP. The problem is, we don't have known data regarding those routes. However, the Overland Route should serve as a warning with regard to similar situations.

Mike Brock


Re: Freight car distribution

Stokes John
 

This is the other factor in this essentially impossible and largely meaningless exercise in trying to figure out how many cars of each type would typically be seen on a train in the time period selected and then extrapolate that information to one's model railroad. Who has 1000 + cars? Who has the full mix of car types within box car classes alone and who has a layout on which to run full length freight trains? Not very many of us at all. So the averages, which are a rule of thumb perhaps but otherwise are just a mental exercise, don't really apply to any actual person's layout. Far too many, many variables in a national system, with the almost infinite perambulations of individual railroads, prototype and model, for these figures to have real meaning to a modeler. Again, the best and perhaps only lesson is to try to avoid the "iconic" cars when they were actually few in number, and balance your cars, with a good dose of home road cars, depending on what the history of your prototype was at any given time, when they had or didn't have a large fleet or kept it close to home, as in grain shipment time or on dedicated mineral runs.

Reality is not the same as a computer simulation under the rather limited and primitive conditions we are working in here.

It doesn't take a long time looking at photos, for example, of Northern Pacific or Great Northern freight trains and yards to see that at least on the days the pictures were taken, home road equipment often dominated, but the stats say otherwise. Go figure. Glad you are having fun with all this, Mike.

John Stokes
Bellevue, WA



To: STMFC@yahoogroups.comFrom: brockm@brevard.netDate: Sun, 17 Aug 2008 20:18:51 -0400Subject: Re: [STMFC] Re: Freight car distribution




Tim O'Connor writes:"Good work, Larry! That's what I'm talkin' 'bout!A 40 car train with 9 SP (not counting T&NO) boxcars.."I assume you mean a train with 40 box cars. Actually the 1949 trains averaged 82.3 cars."More than 5 times the 'average' value of1.6."I'm not certain what the 1.6 represents. The actual number is 4.Mike Brock...I never thought statistics could be fun.


Re: Freight car distribution

Tim O'Connor
 

Mike Brock wrote

Larry, could you explain what you are talking about? You show RR [ i.e., SP
excluding T&NO ], number [ number of SP box cars { 27757 } ] Nat'l % [ you
show 4.0% but Tim shoed 3.9% ] and Random % [ 4.01% ]. What is the
derivation of the random %?
Mike, he ran 100,000 iterations of a 40 car box car train, composed
of cars chosen randomly from every possible prototype. The National
% is obvious, and then he finds the AVERAGE % found for that railroad
in the random consists. What is not obvious about this?


I tallied the maximum number of cars for each railroad over all the
iterations. In a 40 boxcar train, the average number of cars would be
40 times the national percentage shown in the above table."
Why do you say that?
Because he described it obscurely. He simply kept track of the largest
number of cars seen for each reporting mark in the 100,000 trains. Is
this not also obvious?


Well...actually that's not so at all. The correct number is 4. 136/34
If you use real...rather than theoretical data.
Real what? 136 box cars? 136 trains? 136 days? 136 train consists?

Larry's example was PURELY theoretical, and he made an excellent point.
I guess some people just don't get it.


We know that there were 4 of 34 trains...11.76%...of the trains with
far more than 9 SP bx cars.
Mike, you are having trouble grasping the idea. Larry has presented
100,00 theoretical trains, of fixed length, of random composition.
You persist with your miniscule sample of 34 actual trains of
varying length and composition of different sorts of cars (not just
box cars).


The 1953 data shows the "infamous" train with 36 or more SP box cars
[not T&NO ].
Yes, but I will argue that the Overland Route for the UP and SP was
a 'home road extension' in that each road was highly dependent on the
other for traffic. Therefore we can discount the presence of SP as
well as UP cars in all trains over Sherman Hill, for the purposes of
this discussion. This is exactly the "skew" that each layout has to
consider.

Tim O'Connor

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