Geometric Design of Highways and Streets 6 Edition
Highway engineers, as designers, strive to meet the needs of highway users while maintaining the integrity
of the environment. unique combinations of design controls and constraints that are often conflicting
call for unique design solutions. A Policy on Geometric Design of Highways and Streets provides guidance
based on established practices that are supplemented by recent research. This document is also intended
as a comprehensive reference manual to assist in administrative, planning, and educational efforts
pertaining to design formulation.
Design values are presented in this document in both metric and u.S. customary units and were developed
independently within each system. The relationship between the metric and u.S. customary values is
neither an exact (soft) conversion nor a completely rationalized (hard) conversion; and the use of brackets
around u.S. Customary values does not indicate as in some AASHTO publications that these are soft
conversions. The metric values are those that would have been used had the policy been presented exclusively
in metric units; the u.S. customary values are those that would have been used if the policy had
been presented exclusively in u.S. customary units. Therefore, the user is advised to work entirely in one
system and not attempt to convert directly between the two.