Wherever bridges or trestles over rivers and streams would be required on the route locations as projected they are shown on these diagrams. At intersections of the projected lines with all other roads and railroads the diagrams indicate the probable manner in which the grades at the intersection would be separated, whether by underpass or overpass.
The estimated 1937 traffic on all cross roads at their points of intersection with the projected route locations is shown by the length, to an indicated traffic scale, of short vertical bars appropriately positioned above the points at which the corresponding cross roads intersect the projected line. Consistent with the indications of this traffic scale, numerous lightly traveled cross roads are shown as scheduled for closing if the projected road is built, their traffic to be diverted to nearby crossings.
Finally, the straight-line diagrams and the tabulated information on which they are based show the location of all proposed access points on the routes as located, and their relation to cities and towns and important intersecting roads.
Coupled with the large-scale maps showing the approximate geographic position and courses of the routes, the diagrammed and tabulated decisions with respect to the design of the roads serve as the basis for the estimated cost of the proposed facilities.
ESTIMATED COSTS OF RIGHT-OF-WAY AND CONSTRUCTION
The estimates of right-of-way and construction costs were made and compiled in the several district offices of the Bureau of Public Roads in accordance with uniform basic decisions laid down by the Chief of Bureau. All unit costs and construction quantities used were based on intimate knowledge of all local conditions and the current prices paid for the various items of work.
Right-of-way.—Right-of-way, exclusive of accesses, was assumed to consist of 36 acres per mile for rural areas and a minimum of 19 acres per mile for urban areas. These values are based on widths of 300 feet and 160 feet, respectively. For each access point, from 3 to 10 acres were added for two-lane construction and from 10 to 15 acres were added for four-lane construction. Property damage, if any, was estimated and added as a lump sum between control points. Right-of-way and property damage varied from a minimum of $5 per acre to $50,000 per acre.
Where it was necessary to relocate existing highways or construct new service roads between control points so that traffic on closed cross roads could be rerouted to nearby separated crossings or to restore service on public roads occupied by the new construction, estimates were made of the mileage involved and the costs per mile.
Grading. Estimates of grading quantities were based upon a uniform schedule of earthwork volumes per mile corresponding to five general types of topography, from which an appropriate selection was made for each varying section of the located lines.
