Bruce Smith wrote:

It is VERY important to differentiate between "home road cars" on the home road and home road boxcars... On the PRR the former was around 50% for most of the modern steam era and while we do not have a precise figure for the latter (boxcars), that number is closer to 20-25%, exactly what was seen in the C&S figures. Just another piece of the puzzle that supports the national fleet model ;^)

I agree with Bruce. In the conductor time book data I have for SP's Coast Line during 1948-1952, home road box cars were 29 percent, and T&NO box cars (closely allied, of course) another 7 percent, or a total of 36 percent of all BOX cars observed. But this particular conductor worked a lot of extra trains, especially reefer extras (empties one way, loads the other) in peak harvest season, and beet trains (again, empties and loads) in sugar beet harvest season. Those two car types dominate box cars, even though on the SP as a whole, the converse is true. Any given chunk of data needs to be viewed in context, as Bruce says.
I discussed those time book data and provided details of the data in a series of blog posts entitled "Modeling freight traffic: Coast Line, 1953," especially Parts 6, 7 and 8. Here is a link to Part 8, for anyone interested; it contains links to the two previous posts.

http://modelingthesp.blogspot.com/2011/04/modeling-freight-traffic-coast-line.html

Tony Thompson
2906 Forest Ave., Berkeley, CA 94705
(510) 540-6538; fax, (510) 540-1937;
e-mail: thompson@...