Design Standards

• Memos
  • 2005 Interstate Standards (05/08/2006)
  • 2004 Green Book (02/23/2005)
  • 2001 Green Book (02/15/2002)
  • Design Speed (11/04/1988)
  • Design Speed (08/21/1985)
• Horizontal Clearance and Clear Zone FAQ
• State Roadway Design Manuals
• State Standard Drawings

Title 23 USC 109 provides that design standards for projects on the National Highway System (NHS) must be approved by the Secretary of the U.S. Department of Transportation in cooperation with the State highway departments. The Secretary has delegated this authority to the Federal Highway Administrator.

The State highway departments, working through the American Association of State Highway and Transportation Officials (AASHTO) develop design standards through a series of committees and task forces. FHWA contributes to the development of the design standards through membership on these working units, sponsoring and participating in research efforts, and many other initiatives. Following development of the design standards, FHWA uses a formal rulemaking process to adopt those it considers suitable for application on the NHS.

The design standards currently adopted by the FHWA can be found at 23 CFR 625. Additional design guides and references can be found in the Federal-Aid Policy Guide, Non-regulatory Supplement NS 23 CFR 625, paragraph 16. The CFR and Non-regulatory Supplement do not include the standards themselves, but rather a list of publications which contain the standards. Probably the most frequently used document in 23 CFR 625 is A Policy on Geometric Design of Highways and Streets. This 1000+ page document, sometimes called the Green Book because of the color of its cover, is published by AASHTO and can be found in many public libraries. The Green Book can also be purchased from the AASHTO web site noted above.

The Interstate System, all of which is included as part of the NHS, has a special set of standards as listed in 23 CFR 625. The standards, A Policy on Design Standards -- Interstate System, are also published by AASHTO and available at their web site.

Projects off the NHS

Title 23 USC 109 provides that projects (other than highway projects on the NHS) shall be designed, constructed, operated, and maintained in accordance with State laws, regulations, directives, safety standards, design standards, and construction standards.