These Data Are Collected By The Bureau Of Transport Economics And Statistics From Reports Of Individual Class I Railroads. Switching And Terminal Companies Are Included. Additions Refer To New Facilities, Such As Tracks, Building And Other Structures; And Additions To These Facilities. Betterments Comprise Improvements To Existing Facilities Such As The Application Of Heavier Rail In Tracks, Strengthening Of Bridges By Substitution Of Heavier Members, And Construction Of Superior Floors Or Roofs In Buildings. These Data Are Also Published In"Historical Statistics Of The United States, Colonial Times To 1957," Bureau Of The Census, Series Q105. Source: Interstate Commerce Commission, 1921-1955:"Railroad Transportation, A Statistical Record, " Association Of American Railroads, Bureau Of Railway Economics, December 1956. 1956-1963:"Selected Income And Balance-Sheet Items Of Class I Railroads In The U.S., " Bureau Of Transport Economics And Statistics, Interstate Commerce Commission, Statement No. M-125, December Issues Through 1961; No. Q-125, 4Th Quarter Issues For Later Figures.
This NBER data series a02231 appears on the NBER website in Chapter 2 at http://www.nber.org/databases/macrohistory/contents/chapter02.html.
NBER Indicator: a02231
Release: NBER Macrohistory Database
National Bureau of Economic Research, Capital Expenditures For Additions and Betterments, Roadway and Structures, Class I Railroads for United States [A02231USA550NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A02231USA550NNBR/, October 7, 2015.