Historical Statistics of the United States Millennial Edition Online

		Df1089	Df1090¹	Df1091
		Average miles of road	Revenue passenger-miles	Employees
Row	Year	Miles	Million passenger-miles	Number
1	1915	----	8,925	----
2	1916	----	9,285	----
3	1917	----	----	----
4	1918	----	10,679	----
5	1919	----	13,720	----

6	1920	----	14,334	----
7	1921	----	11,295	----
8	1922	123,547	11,759	19,066
9	1923	124,794	12,982	23,579
10	1924	124,795	13,082	25,091

11	1925	126,840	14,016	26,919
12	1926	126,907	14,409	26,185
13	1927	123,334	14,099	27,359
14	1928	128,753	13,938	26,815
15	1929	130,019	14,059	29,250

16	1930	129,578	12,516	26,165
17	1931	125,703	9,891	22,546
18	1932	118,061	6,757	17,132
19	1933	112,298	6,142	15,887
20	1934	112,420	6,891	19,066

21	1935	112,117	7,146	20,436
22	1936	111,522	8,355	21,711
23	1937	111,507	9,170	23,406
24	1938	110,728	8,270	20,750
25	1939	109,886	8,485	21,335

26	1940	109,595	8,214	20,877
27	1941	108,034	10,070	22,704
28	1942	106,408	19,072	26,591
29	1943	104,128	25,891	33,182
30	1944	103,766	28,267	39,703

31	1945	95,765	27,276	41,601
32	1946	100,653	20,672	36,982
33	1947	105,950	13,516	29,046
34	1948	104,940	12,172	23,724
35	1949	104,287	10,544	22,286

36	1950	102,722	10,558	22,820
37	1951	99,592	9,893	23,862
38	1952	96,390	9,336	22,588
39	1953	94,518	8,200	21,529
40	1954	91,920	7,271	19,866

41	1955	89,124	6,882	18,061
42	1956	87,472	6,630	16,793
43	1957	85,068	5,388	14,890
44	1958	79,555	4,300	10,234
45	1959	71,448	3,462	8,020

46	1960	67,467	3,358	7,320
47	1961	63,035	3,046	6,688
48	1962	61,278	2,905	6,392
49	1963	59,798	2,516	5,902
50	1964	52,994	2,218	5,544

51	1965	51,057	2,014	5,347
52	1966	45,807	1,969	4,905
53	1967	42,713	1,434	4,179
54	1968	33,464	1,002	2,945