A Policy on Geometric Design of Highways and Streets
|Publication Date:||1 January 2018|
Public works projects of all scales are more sensitive to funding than ever before. In many cases, cost magnitude and cost effectiveness play increasingly large roles in scoping projects. Often, reconstruction projects are limited in scope or available funding, or may be affected by physical constraints or social or environmental considerations. In some locations, especially constrained locations, designing to the criteria recommended herein simply is not feasible. Adaptive, flexible, and cost-effective designs customized to each project context are encouraged. Flexibility in the application of design criteria herein is recommended to encourage a sustainable approach to highway design decision making by weighing and balancing choices among the environmental, economic, and social aspects while meeting the project's performance objectives.
Designers should recognize the joint use of transportation corridors by motorists, pedestrians, bicyclists, public transit, and freight vehicles. Designers are encouraged to consider not only vehicular movement, but also movement of people, distribution of goods, and provision of essential services. A more comprehensive transportation program is thereby emphasized.
A Policy on Geometric Design of Highways and Streets provides geometric design guidance based on established practices that are supplemented by recent research. This document is intended as a comprehensive reference manual to assist in administrative, planning, and educational efforts pertaining to design formulation. This policy is not intended to be a prescriptive design manual that supersedes engineering judgment by the knowledgeable design professional.
The design concepts and criteria in this policy are intended for use when designing new construction projects on new location or designing reconstruction projects on an existing location. Projects on existing roads particularly call for a flexible, performance-based approach to design. The policy also encourages flexible design, which emphasizes the role of the planner and designer in determining appropriate design dimensions based on project-specific conditions and existing and future roadway performance more than on meeting specific nominal design criteria. This publication is not intended as a policy for resurfacing, restoration, or rehabilitation (3R); traffic engineering; safety; and preventive maintenance-type projects that include very minor or no roadway work. When designing 3R projects, the designer should refer to the design guidelines presented in NCHRP Report 876, Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects, for more information. NCHRP Report 876 was developed as a replacement for TRB Special Report 214, Designing Safer Roads: Practices for Resurfacing, Restoration, and Rehabilitation.