Data Include Unserviceable Units. Source: Computed By NBER By Dividing Series 03003 (Revenue Ton-Miles) By Series 01253 (Total Freight Cars On Line).
This NBER data series m03067 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03067
Release: NBER Macrohistory Database
National Bureau of Economic Research, Revenue Ton-Miles Per Freight Car On Line for United States [M03067USM604SNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M03067USM604SNBR/, November 30, 2015.