Page:Highway Needs of the National Defense.pdf/46

30 the deficiencies existing were appraised by applying to the determined conditions uniform standards relating to each significant element of design.

ESTABLISHMENT OF STANDARDS

The standards to be applied were previously agreed upon by the Public Roads Administration and a committee of State highway officials appointed by the American Association of State Highway Officials. In general, the standards agreed upon are identical with those adopted by the association August 1, 1945, to govern the design of highways included in the interstate system. In certain respects, however, it was necessary to define more exactly the previously agreed standards in order to facilitate their uniform application for the purposes of this report.

The standards adopted bv the association in 1945 contemplate the provision of design adequate for the service of traffic as it may be expected to develop in a period of 20 years subsequent to the construction of each section of the system as it is improved. This necessitates an estimate of future traffic growth which can be undertaken with reasonable assurance only in the light of specific consideration of the potentialities of each section of the system.

For the purposes of this report such specific consideration has been impracticable. The standards have therefore been applied to all sections of the system in relation to their traffic in 1948. Appraisal of the deficiencies of the existing roads and bridges has been based upon the actual 1948 traffic as reported. The improvements contemplated to eliminate the determined deficiencies, which improvements form the basis of the cost estimates reported, have been planned to serve with adequacy the traffic which it is judged would have used each section of the system, had it been so improved in 1948.

THE STANDARDS APPLIED

The principal standards so applied, both for the determination of deficiencies and the estimation of costs of required improvements, are briefly described here.

Traffic basis

The design shall be such as to accommodate traffic density of the thirtieth highest hour of 1948.

Design speed

Design speed shall be in accordance with the following: