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It is impossible, on the basis of the very general studies made by the Committee, to venture even an approximate estimate of the total cost of building the entire interregional system to the standards recommended. To be of any value whatever, such an estimate would necessarily have to be predicated upon a far more exact determination of the location of the routes and of the manifold conditions of topography, soil, frequency of road intersection, traffic diversion, property affected, etc., than it has been possible to undertake. Had it been possible to make such precise determinations, moreover, the usefulness and validity of an estimate of the ultimate cost of a construction program that must inevitably extend over a period of perhaps 20 years and be affected by unpredictable changes in the general economy, in the habits and desires of the people, in the character of vehicles, and in other circumstances, would still be highly questionable.

Construction to the standards recommended will certainly be expensive beyond the common experience in building most of the ordinary existing roads and streets, but the merit of the expenditure is to be judged not by such a comparison but rather by the value of the advantages to be gained in traffic facilitation, in reduced costs of vehicle operation, and in lowered accident rates.

COSTS IN RURAL AREAS

A large part of the construction in rural areas, however, will not be highly expensive. As previously stated, the traffic in 1941 was less than 1,000 vehicles a day on existing roads conforming to approximately 21 percent of the total rural mileage of the system. The system as improved in these sections will attract a somewhat greater traffic, but the increase to be expected will not materially affect the design of the new facilities. Sections of the system of this general order of traffic volume can presently be built to the standards proposed at costs ranging between $40,000 and $60,000 per mile.

Rural sections of the system serving traffic averaging from 1,000 to 2,000 vehicles per day, a range characterizing 32 percent of the existing closely conforming roads in 1941, can probably be built to the proposed standards, at present prices, for $50,000 to $70,000 per mile.

These two traffic ranges, it will be noted, cover half of the entire mileage of rural roads approximating routes of the recommended system.

The existing roads that served traffic between 2,000 and 3,000 vehicles per day in 1941 made up 21 percent of the total; and the mileage of the system as built that would probably carry traffic of this order of density would doubtless be a somewhat larger percentage of the total. The cost of these sections would vary considerably according to the extent to which, on individual sections, it is necessary, in conformity with the standards proposed, to employ divided four-lane construction. Under the most favorable conditions, the cost of such sections would probably be little if at all greater than that of the sections serving traffic of between 1,000 and 2,000 vehicles per day. Where extensive four-lane construction is required, and on sections serving traffic approaching the upper limit of the range, the cost might closely approximate that of completely four-laned sections.