scope:

PREFACE

This Policy was developed as part of the continuing work of the Standing Committee on Highways. The Committee, then titled the Committee on Planning and Design Policies, was established in 1937 to formulate and recommend highway engineering policies. It has developed A Policy on Geometric Design of Rural Highways, 1954 and 1965 editions, A Policy on Arterial Highways in Urban Areas, 1957, A Policy on Design of Urban Highways and Arterial Streets, 1973, Geometric Design Standards for the National System of Interstate and Defense Highways, 1956 and 1967, Geometric Design Standards for Highways Other Than Freeways, 1969, A Policy on Geometric Design of Highways and Streets, 1984 and 1990, A Policy on Design Standards- Interstate System, 1991, and a number of other AASHO and AASHTO policy and "guide" publications.

An AASHTO publication is typically developed through the following steps: (1) The Committee selects subjects and broad outlines of material to be covered. (2) The appropriate subcommittee and its task forces, in this case the Subcommittee on Design and its Task Force on Geometric Design, assemble and analyze relevant data and prepare a tentative draft. Working meetings are held and revised drafts are prepared, as necessary, and reviewed by the Subcommittee, until agreement is reached. (3) The manuscript is then submitted for Standing Committee on Highways approval, and then Executive Committee approval. Standards and policies must be adopted by a two-thirds vote by the Member Departments before publication. During the developmental process, comments were sought and considered from all the States, the Federal Highway Administration, and representatives of the American Public Works Association, the National Association of County Engineers, the National League of Cities, and other interested parties.

The Omnibus Trade and Competitiveness Act of 1988 amended by the Metric Conversion Act of 1975 required each federal agency to convert to the metric system. In response the U. S. Department of Transportation, Federal Highway Administration, established September 30, 1996 as the date for metrication of plans, specifications, and estimates for projects constructed with federal aid. This action required AASHTO to metricate this policy. ASTM E380 Standard Practice for Use of the Intei-national System of Units (SI) was adopted by FHWA as the standard to guide metric conversion. Following the procedures outlined above, the Task Force on Geometric Design met in 1992 to begin work which resulted in the publication in 1993 of the Interim Selected Metric Values for Geometric Design as an addendum to the 1990 Policy and subsequently this current edition. This new Policy supersedes the Interim Guide. A continuing effort will be maintained by the Subcommittee on Design to keep the Policy up to date with future developments in geometric design.