On older employee timetables (and other sources) siding capacity was usually given in car lengths. With the passage of time, "average" cars got longer and as a result the car capacity of unaltered sidings seems to have been reduced. I've been unable to locate any Frisco source which actually states what values were used for car length at any given date. Does anyone have this information?
There must be a formula for figuring train lengths with "today's" freight cars?? I've heard BNSF and KCS dispatchers on my scanner reading train orders and they'll say something like:"____loads, ____emptys and____car lengths." And the loads+emptys don't add up. I'm sure a current or former RR employee can shed a lot more light on this subject than a railfan/modeler like me.
To use the KCS example, in the "system special instructions" section of their System Timetable #1 (1996) it states "The length of a siding is measured from clearance point to clearance point. Capacity of auxillary tracks in car lengths is based on 50 foot cars." Even in our computer age I doubt if they use the exact figures of each car to figure lengths of anything but, perhaps unit coal trains. Maybe they just use that same 50 feet "average" length? Obviously in the distant past they would have used much less than a 50 feet average car length.
Since they also used "car capacity" I'm sure Frisco published this same type of information, for the "benefit" of employees, at various times. I've been told that for many years Frisco siding capacity was figured at 40 feet/car. Prior to that smaller values seem to have been used. In the 1970's it may have been more. I'm sure the lengths changed from time to time. I'm trying to find the approximate dates that the changes were made (and of course what the new value for length was) in order to estimate spur and siding lengths in feet. On a long spur track like one at Bonanza, AR (Central Division, 1944) with a 280 car capacity, a difference of even five feet in car length is significant.