I assume you are talking about the Slumbercoaches. The CBQ and NP utilized the combined eight cars very well. One Slumbercoach that came in on the eastbound Denver Zephyr was switched out of that consist and inserted into the westbound North Coast Limited that departed at 1210PM assuming no missed connections. Simarily the Slumbercoach that arrived about 2PM on the NCL was switched into the outbound DZ. At the beginning the DZ had two Slumbercoaches, one for Denver and the other one for Colorado Springs. The quote was probably actually meaning the eight Slumbercoaches. It is approximately 1000 miles from Chicago to Denver and 2200 miles from Chicago to Seattle. Four Slumbercoaches for the two DZ's and four for the NCL. My quick math says that the eight cars ran about 6200 miles per day. Please correct my math as math is not my strength.
As information, the NP purchased the four NYC cars, three B&O cars, and one TP car. One of the NP cars was purchased by the CBQ to equalize mileage.
Ed Burns
Retired NP-BN-,etc from Northtown, MN