and so doing saves $42,000,000 in the construction cost at the expense of 4 or 5 miles of extra distance for traffic moving between Chicago and Detroit. The western north–south route takes a protected valley course for the most part from border to border, within easy reach of all the coastal cities.
The northern east–west route joins the hub of New England with Seattle, northernmost of west coast cities, and in its intermediate course first serves Cleveland, Chicago, and the other Great Lakes cities and the Twin Cities of Minnesota and then follows almost an air line through North Dakota and Montana.
The central east–west route begins at a junction with the Atlantic coast route, which can be reached conveniently from New York and Philadelphia, and thence follows a very direct line to San Francisco. The line first chosen for this route diverged from the final line southwestward at a point near Indianapolis, to pass close to St. Louis and Kansas City, and then followed the Missouri River northward to a point between Lincoln and Omaha, Nebr., where it entered the valley of the Platte River and thence followed the line of the historic Oregon Trail and Overland Route into Wyoming. The change to the present direct route between points near Indianapolis and Denver follows the consensus of advice received from the responsible State highway officials of all the States affected.
The southern east–west route begins near Charleston, S. C., and runs very directly through the southern tier of States to Los Angeles. It crosses the eastern north–south route at a point that nicely compromises the claims of the southern coastal cities, which there have convenient access to it. It passes near Atlanta, Birmingham, Montgomery, and Jackson, and heads directly toward Dallas and Fort Worth in Texas, whence, avoiding the Big Bend of the Rio Grande River, it passes just north of El Paso and on to its western terminus.
OPTIMUM LOCATION FOR COLLECTION OF TOLLS
Finally, and subject to a proper balance of all previous considerations, it was the intention so to locate the several routes, as to achieve an optimum condition in respect to toll collections. The results in this respect are set forth in great detail in subsequent pages. It is sufficient at this point to state that it is believed that no substantial change in the chosen lines, reasonably consistent with the several considerations previously discussed, would improve upon the potential earning power of the lines selected.
METHOD FOLLOWED IN SELECTION OF THE PROPOSED ROUTES
In January 1938 the first traffic map of the United States was compiled by the Bureau of Public Roads from the latest data then obtainable from State traffic flow charts and available tabulations, most of which had been prepared in connection with the highway planning surveys. In January 1939 this map was revised to conform with more complete and detailed information, and the revised map is reproduced in plate 7.
The traffic flow represented is that of the year 1937 on routes of the United States highway system and other main-traveled highways. Bands of varying width, centered upon the approximate lines of the various highways, indicate by their scaled width at all points the vol-
