A Policy on Design Standards-Interstate System
|Publication Date:||1 May 2016|
The Dwight D. Eisenhower National System of Interstate and Defense Highways (Interstate) is the most important highway system in the United States. It carries more traffic per mile (kilometer) than any other comparable national system and includes the roads of greatest significance to the economic welfare and defense of the nation. The highways of this system are to be designed in keeping with their importance as the backbone of the nation's highway systems. To this end, they are designed to provide safety and mobility for predicted growth in traffic.
These objectives can be realized by conscientious attention to design. The following minimum standards apply to Interstate highway segments constructed on new right-of-way and segments undergoing reconstruction along existing right-of-way. The geometric design standards used for resurfacing, restoration, and rehabilitation (3R) projects may be the AASHTO Interstate standards that were in effect at the time of original construction or inclusion into the Interstate system.
Design values are presented in this document in both U.S. customary and metric units and were developed independently within each system of units. The relationship is neither exact (soft) nor a completely rationalized (hard) conversion. The values are those that would have been presented in either system. Therefore, the user is advised to work entirely in one system and not attempt to convert directly between the two. In addition, all projects, including 3R, or elements of projects that retain existing geometrics meeting the minimum standards for the selected design speed in one system of units are considered in compliance with comparable design speed standards in the other.
The current editions of AASHTO's A Policy on Geometric Design of Highways and Streets ("The Green Book") and the AASHTO LRFD Bridge Design Specifications shall be used as design guides where they do not conflict with these standards.