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Bridges & Structures

Contact information was updated by Vertical Clearance Memo on 4/15/09.

Subject: ACTION: Vertical Clearance, Interstate System Coordination of Design Exceptions Date: August 15, 1997
From: Associate Administrator for Program Development Reply to Attn. of: HNG-14
To: Regional Administrators
Federal Lands Highway Program Administrator

For almost 30 years, the Federal Highway Administration (FHWA) and the Military Traffic Management Command Transportation Engineering Agency (MTMCTEA) of the Department of Defense (DOD) have cooperated to meet the demands of military traffic on the Interstate System, particularly in the area of vertical clearances. This need has been met with the adoption of standards by FHWA for vertical clearance on the Interstate that require a clear height of structures over the entire roadway width, including the useable width of shoulder, of 4.9 meters for the rural Interstate. In urban areas, the 4.9-meter clearance is applied to a single route, with other Interstate routings in the urban area having at least a 4.3-meter vertical clearance.

In 1960, at the request of the DOD, and with the cooperation of the States, the above standards were established to accommodate military traffic on the Interstate. At that time, a large number of structures on the Interstate, constructed under previous criteria, existed which did not conform to the new minimum standard. The correction of all these deficiencies could not be economically justified. Consequently, in 1969, the MTMCTEA, the American Association of State Highway and Transportation Officials (AASHTO) (then AASHO) and the FHWA agreed to concentrate on a subset of the Interstate judged to be priority routes. The subset contained a significantly smaller number of deficient structures on 41 842 kilometers of the Interstate. The 41 842 kilometer priority network served about 95 percent of the major military installations.

Since then, the MTMCTEA has developed and continues to refine the Strategic Highway Network (STRAHNET). The STRAHNET report dated January 1991 was distributed to Regional Federal Highway Administrators by memorandum from the Director, Office of Environment and Planning dated March 22, 1991. Since 1991, there have been a few changes made to STRAHNET. These changes have been coordinated with the States and the field offices. Maps delineating the changes were distributed to the affected regional offices by HEP-l0. The STRAHNET is a system of highways that provides defense access, continuity and emergency capabilities for movements of personnel and equipment in both peacetime and wartime. The STRAHNET was based on quantifiable DOD requirements, addressing their peacetime, wartime, strategic, and oversize/overweight highway demands. The network consists of approximately 96 000 kilometers of highway. The STRAHNET has been incorporated into the National Highway System (NHS). Almost 75 percent of the system in the continental United States (about 70 000 kilometers) consists of roadways on the Dwight D. Eisenhower National System of Interstate and Defense Highways.

The currently established procedures require the FHWA to coordinate with the MTMCTEA when a clear height of structures of less than 4.9 meters is created as the result of a construction project or the project does not provide for the correction of existing substandard vertical clearance on the 41 842-kilometer priority network prior to approving the exception. For routes not on the priority network, coordination is not required although the FHWA policy provides that the MTMCTEA be notified of all exceptions to vertical clearance on the remainder of the Interstate System. The approval action for exceptions to vertical clearance has been delegated to the field offices, which can contact the MTMCTEA directly. When the State highway agency (SHA) has approval authority for design exceptions under one of the 23 U.S.C. 106(b) exemption provisions, coordination with the MTMCTEA is still required and may be accomplished through the FHWA or directly with the MTMCTEA.

The development of the STRAHNET, the establishment of Power Projection Platforms, base realignments, and the evolving role of the military have created a need to revise coordination procedures between the MTMCTEA and the FHWA, concerning exceptions to the vertical clearance requirements on the Interstate System. Therefore, the FHWA and the MTMCTEA have agreed that all exceptions to the 4.9-meter vertical clearance standard for the rural Interstate and the single routing in urban areas, whether it is a new construction project, a project that does not provide for correction of an existing substandard condition, or a project which creates a substandard condition at an existing structure, will be coordinated with the MTMCTEA beginning upon receipt of this memorandum. This agreement extends to the full roadway width including shoulders for the through lanes, as well as ramps and collector-distributor roadways in Interstate-to-Interstate interchanges. This change in effect eliminates the 41 842-kilometer priority network as a separate subset of the Interstate System. The revised coordination procedures do not change the standards adopted for the Interstate enumerated in "A Policy on Design Standards - Interstate System," AASHTO, July 1991, or the delegations of authority in FHWA Order M1100.1A.

A number of toll roads are part of STRAHNET by virtue of being incorporated into the Interstate System under the former provisions of Section 129(b) of Title 23, United States Code. While the FHWA does not have any particular "leverage" on the toll authorities to comply with Federal standards on non-federally funded projects, it is expected that the SHA's have established appropriate procedures to assure that proposed changes or alterations of the toll road will meet applicable policies established for the Interstate System. The working relationship should ensure the needs of the military are considered and that necessary coordination occurs.

A request for coordination may be forwarded to the MTMCTEA at any time during project development prior to taking any action on the design exception. It should include a time period of 10 working days (after receipt) for action on the request. The office initiating a request for coordination to the MTMCTEA should verify receipt of the request by telephone or fax. If the MTMCTEA does not respond within the time frame, the FHWA should conclude that the MTMCTEA does not have any concerns with the proposed exception. If comments are forthcoming, the FHWA and the SHA will consider mitigation to the extent feasible.

A request for coordination should be addressed to:

Military Traffic Management Command Transportation Engineering Agency (MTMCTEA)
720 Thimble Shoals Boulevard, Suite 130 Newport News, VA 23606-2574
(Telephone: 757-599-1117, Fax: 757-599-1560)

The Federal Aid Policy Guide Non-regulatory Supplement, 23 CFR 625, Paragraph 7 of Transmittal 13 dated July 21, 1995, will be revised as appropriate at the earliest opportunity. Questions regarding this memorandum should be directed to William A. Prosser at 202-366-1332, or Robert C. Schlicht at 202-366-1317.

Thomas J. Ptak

Updated: 06/26/2013
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000