Design

Superseded by the 2011 Green Book https://www.fhwa.dot.gov/design/standards/151112.cfm on 11/12/2015

U.S. Department of Transportation Federal Highway Administration

MEMORANDUM

Attached for your information is a copy of the Final Rule for incorporating the new AASHTO publication "A Policy on Geometric Design of Highways and Streets" into 23 CFR 625. The adoption of the new policy will supercede all but one of the previous AASHTO policies and guides dealing with the geometric design of new construction and reconstruction projects. "A Policy on Design Standards - Interstate System" will continue in effect.

The effective date of the formal adoption will be 30 days from the date of the publication of the notice in the Federal Register.

Much of the material contained in the superceded guides has been incorporated into the policy. This elevates its stature from advisory to policy status. While material from the superceded guides, as well as much other valuable criteria and information is included in the new policy, only certain portions should be viewed as controlling criteria. Therefore, those criteria related to design speed, lane and shoulder widths, bridge widths, structural capacity, horizontal and vertical alignment, grades, stopping sight distance, cross slopes, superelevation, and horizontal and vertical clearances contained or referenced in the functional Chapters VI , VII, and VIII are to be the controlling criteria and require formal design exceptions when not met. In the absence of material covering controlling criteria in the functional chapters material is to be sought in Chapters III and IV. Criteria in Chapter V, Local Roads and Streets, apply only to off-system projects.

In a number of instances, a range of acceptable values has replaced specific values of minimum, maximum, and desirable contained in the superceded policies and guides. The result is that specific limiting criteria may not be clearly apparent. It is the FHWA policy that the lowest or highest value of the range, whichever is appropriate, is to be considered as the minimum or maximum acceptable for design of Federal-aid projects. This is consistent with AASHTO's intent as reflected by the statement in the "Foreward": "Minimum values are either given or implied by the lower figure in a given range of values." A range of values is also available for design speed. Design speed is to be selected to equal or exceed the posted or regulatory speed limit of the completed facility.

Insofar as the new policy represents the state-of-the-practice and, as such, should be implemented as quickly and completely as possible, every effort should be made to incorporate new provisions as promptly and on as many projects as possible. Each Division Administrator should discuss the implementation of the policy with the respective State and reach an agreement as to the application of the new policy to ongoing projects.

Additionally, since the adoption of new policy may require changes in the States' formal design standards, policies and other procedures, a 1-year period (from the effective date of incorporation in 23 CFR 625) is established for accomplishing the following:

1. Review States' existing design standards and policies and affect necessary changes in them.
2. Review and modify, as necessary, design standards and policies contained in approved Certification Acceptance Plans.
3. Review and modify, as needed, design standards and policies contained in approved Secondary Road Plans. (A discussion of the new criteria applicable to secondary road projects is attached for your information and use.)
4. In those cases where the Secondary Road Plan is also applicable to off-system and other projects, the effect of any changes in design criteria on those projects should be considered.

Revision necessitated by the above reviews should be accomplished in accordance with existing policies and delegations of authority.

/s/ original signed by
E. Dean Carlson

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