Page:Highway Needs of the National Defense.pdf/47

Rh Curvature

Curvature shall be related to design speed as follows:

Stopping sight distance

Applicable to all sections, the road surface ahead shall be visible for distances varying with the design speed as follows:

Passing sight distance

Applicable to two-lane sections only, the following criteria are to be observed:


 * 1) In any 6,000 feet of roadway length, the road surface shall be visible for at least 1,500 feet ahead on a roadway length of at least 1,000 feet.
 * 2) The minimum percentage of the length of roadway on which the road surface is visible 1,500 feet ahead shall vary with the density of two-direction traffic in the thirtieth highest hour, as follows:

Gradient

Maximum gradient preferably shall not exceed 5 percent, and in no case shall exceed 6 percent.

Supporting strength

The strength of the road surfaces and foundations shall be adequate for the support of 18,000-pound axle loads in the frequency to be expected.

Right-of-way

Right-of-way width for two-lane rural highways shall preferably be 200 feet, with a minimum of 120 feet. For four-lane rural highways, 250 feet is desirable and 150 feet minimum.