Low-volume rural roads, those carrying 400 vehicles per day or less, constitute two-thirds of the total U.S. highway system. Their key importance to the national transportation objective cannot be denied. Not only are they the largest single class of highway, but they are also the vital link of the nation's agricultural economy. National guidelines for the design of low-volume rural roads are contained in the 1971 AASHTO publication "Geometric Design Guide for Local Roads and Streets." For traffic control devices, the basic guidelines are presented in the "Manual of Uniform Traffic Control Devices." But, because these national guidelines reflect the safety needs of primary highways, their application to the reconstruction of existing low-volume rural roads is continually being questioned in a time when local highway agencies must spend a majority of their limited funds for highway maintenance. This research was undertaken to reevaluate the safety needs on low-volume rural roads. On the basis of a series of functional analyses relating safety performance to specific design and operational elements, a set of revised guidelines was developed. The revised guidelines apply to total roadway width, horizontal curvature, roadside design, speed signs, curve warning signs, centerline markings, and no-passing stripes. These guidelines are proposed to supplement the existing national policies with each revised guidelines either replacing or clarifying the existing national guideline. The widespread application of the revised guidelines should provide for more consistent design and traffic control of low-volume rural roads consonant with a rational balance between highway investment, highway safety, and traffic service. (Author/publisher)
Abstract