I. Intercity freight traffic by public and private carriers and United States population, years 1929 to 1956
! Includes mail and express.
Includes Canadian and overseas traffic on the Great Lakes.
Excludes coastwise and intercoastal traffic.
'Preliminary.
Sources: Col. 2, 1929-38: Bureau of Railway Economics, AAR; 1939-56: Annual Report of the Interstate
Commerce Commission. Cols. 3 and 4, Annual Reports of Chief of Engineers, U. S. Army. Col. 5, 1929:
Estimated by Bureau of Railway Economics, based on motor truck registrations; 1930-56 American Trucking
Trends, American Trucking Association. Col. 6, 1929-38: Estimated by Bureau of Railway Economics,
AAR; 1939-56: Annual Report of the Interstate Commerce Commission. Col. 7, 1929-33: Estimated by
Bureau of Railway Economics; 1934-56: Statistical Handbook of Civil Aviation, Civil Aeronautics Admin
istration. Col. 9, Bureau of the Census, U. S. Department of Commerce, 1930, 1940, and 1950 as of Apr. 1,
other years estimated as of July 1.