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Superseded by the 11/25/08 Update on Metric Use Requirements for FHWA Documents Memo

FHWA Memorandum to all State Chief Executive Officers
Regarding Metrication Conversion at State Option

To all State Chief Executive Officers:

Since the passage of the Transportation Equity Act for the 21st Century (TEA-21), there have been several inquiries concerning its impact on the Federal Highway Administration's (FHWA) metric conversion policy and progress. In TEA-21, Section 1211(d) removes the target date for metric conversion, thereby allowing the State departments of transportation (DOTs) the option of converting to the International System of Measurements (SI). Section 1211(d) reads as follows:


Section 205(c)(2) of the National Highway System Designation Act of 1995 (23 U.S.C. 109 note; 109 Stat. 577) is amended by striking "Before September 30, 2000, the" and inserting "The".

This change results in the following language:

The Secretary shall not require that any State use or plan to use the metric system with respect to designing or advertising, or preparing plans, specifications, estimates, or other documents, for a Federal-aid highway project eligible for assistance under title 23, United States Code.

In order to better understand the Congressional intent of Section 1211, we have, with the assistance of the Office of Chief Counsel, reviewed the Congressional Record and the TEA-21 conference report. The conference report clearly states that Section 1211(d) does not require any State to modify its current use of the metric system for highways. Comments in the instructions to the conferees indicate that Congress still considers SI to be the preferred system of measurements for the United States and, therefore, Congress did not anticipate that any already converted State would revert as a result of this provision.

We recognize that there are many concerns within the highway community regarding the cost of conversion to SI units and the reason for doing so. One such common comment, for example, is "Why do we need to convert to metric in this country when we do not export highways." The United States however, does export the expertise, technology, and products to construct highways efficiently. In order to do so effectively, we must operate within the global system of measurements. The United States and Myanmar (formerly known as Burma) are the only countries globally which continue to operate predominately in inch-pound units. Companies desiring to compete in the global marketplace are changing to SI. Converting the Federal-aid highway program to SI will assist the highway industry in making this change. In addition, we will expedite technology transfer between national and State-level transportation agencies by moving to the global system of measurements.

Therefore, while FHWA can no longer mandate that States convert to SI, we strongly encourage its continued use. Most of the State DOTs have substantially converted their project development and construction processes to SI. Full conversion by all the State DOTs remains an FHWA goal since it will improve efficiency within the highway construction industry by reducing translation errors and enabling the contractors, consultants, fabricators and material suppliers to return to a single system of units. Recently the Construction Metrication Council (CMC) conducted case studies of 25 SI projects from around the country. The projects varied in size and complexity. Overall, the CMC found that while contractor personnel were initially resistant to SI, especially among workers over 50 years old, those contractors that began and carried the project through in SI had few difficulties. Most of the reported metric problems were related to reverse conversion by contractor personnel. The remaining metric problems were materials supply issues which will decrease as the volume of metric construction increases. Project costs were similar to inch-pound projects of the same size and complexity.

The FHWA believes that it is in the best interest of the highway community to expedite the metrication process and ensure compatibility within the highway industry and with other industries. Reversion to inch-pound units by some States will perpetuate a confusing mix of measurement systems and lengthen the time that the highway contracting industry must operate in a dual unit environment.

Section 1211(d) does not change the requirements placed on the FHWA by Section 5164(b) of the Omnibus Trade and Competitiveness Act of 1988 (Public Law 100-418). Therefore, FHWA will continue to use SI in its daily business activities. Data collection for the Highway Performance Monitoring Program, the Truck Size and Weight Study, and the National Bridge Inventory will continue in SI. In keeping with existing policy, FHWA will use dual units with the SI value first followed by the inch-pound value in parentheses, for correspondence or publications intended for a broad audience which includes the general public (for example, right-of-way or environmental clearance documents, or general information about FHWA programs). All other FHWA documents, including research reports prepared under FHWA planning and research grants, should be in SI only.

Questions about FHWA policy on metric conversion may be referred to either Mr. David Cox (202-366-0355) or Ms. Jennifer Balis (202-366-4631).

Sincerely yours,

Original Signed by:

Kenneth R. Wykle, Federal Highway Administrator

on October 22, 1998

Updated: 06/27/2017
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000