Tim O'Conner writes: I think it's worth some digging down and trying to find out WHY SP box cars were so much more common on the UP than random distribution would predict.
Uhh, Tim have you looked at a map? The SP coming out of Central California did not have to many interchange partners on the east end. Far different then what one finds east of the Mississippi. Fewer interchange partners are going to skew the results in my opinion. What I find interesting in all this is no discussion of UP boxcars on the SP. Did this not happen?