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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - Summer 1995

Metric Conversion: How Soon?

by David Smith

When guillotines fell during the French Revolution, their blades were measured in a new unit of length, centimeters, not inches. The metric system was literally a revolutionary idea, growing out of the Age of Reason and carried along with Napoleon's soldiers many kilometers, not miles, across Europe and from there to countries around the globe.

In our own rational, revolutionary republic, Thomas Jefferson considered the new metric system an admirable advance over old English feet, pints, and pounds. Ben Franklin, John Quincy Adams, and many other leading American thinkers and statesmen agreed. So why hasn't metric happened here?

More than 200 years after the metric system began to spread throughout the world, the United States shares the dubious distinction with Burma and Liberia of being one of only three nations that have not converted to the modern metric system. As the only industrialized nation in the world that has not gone metric, the United States faces serious difficulties in international trade, information exchange, and in engineering and construction projects involving other nations. The Congress, the states, the private sector, and all the appropriate agencies of government, including the Department of Transportation (DOT) and the Federal Highway Administration (FHWA), are trying to rectify this situation.

Americans are stubborn. One of the biggest obstacles to adopting the metric system in the United States has probably been our inherent dislike for anything that divorces us from the "feel" or "sense" of our traditional values for weight, measurement, distance, and speed. An example is the resistance to the transition to metric highway signs.

To gauge public attitudes toward three approaches to changing highway signs to metric, FHWA last summer solicited public comments through a notice in the Federal Register. Given the volume of comments received -- almost 3,000 -- and a 1994 fiscal year prohibition on funding, FHWA decided to delay implementation of sign legend conversion until after 1996. This is just one small example of public foot-dragging on "going" metric.

But make no mistake, we are going metric -- and fairly soon. Do current U.S. efforts to join the modern metric world indicate that we're really going through with it this time? This is a reasonable question.

In 1866, Congress finally legalized the use of the metric system, but 1902 legislation requiring the federal government to use metric exclusively was defeated by a single vote.

In 1960, the international General Conference on Weights and Measures adopted a rationalized, coherent system of metric units, creating the official Système International d'Unités. This system, known as SI in all languages, is the only complete state-of-the-art, maintained and recognized system of units in the world today.

The British are stubborn, too, but Great Britain began a transition to the metric system as a condition of entering the European Common Market in 1965. Canada successfully went metric in the 1970s.

In the United States, our more recent push for metric conversion started with the 1975 Metric Conversion Act that established a U.S. Metric Board to coordinate "voluntary" transition to the metric system. Some industries jumped on the bandwagon. Most did not. The voluntary approach was scrapped.

In 1988, Congress tried a different approach with the Omnibus Trade and Competitiveness Act. One section amended the previous Metric Conversion Act to mandate that all federal agencies implement the metric system in procurement, grants, and other business-related activities. Only two exceptions to this mandatory conversion are allowed: (1) when such use is determined to be impractical and (2) when such use is likely to cause significant inefficiencies or loss of markets for U.S. firms.

A federal agency requesting an exception must prepare a written analysis justifying such action. To date, no program exceptions have been granted by DOT and its agencies.

On July 25, 1991, President Bush issued Executive Order 12770, Metric Usage in Federal Government Programs, mandating the transition to metric measurement for all federal agencies. Finally, U.S. law requires use of the metric system. But when?


FHWA metric poster


What FHWA Is Doing

FHWA began its conversion process in December 1990 by establishing an FHWA metric work group and setting a Sept. 30, 1996, deadline for complete conversion. This planned five-year transition to the metric system involves five activities:

  1. Basic plans and policies. The FHWA Metric Conversion Plan was approved by the DOT Secretary on Oct. 31, 1991, and the Metric Conversion Policy was published in the Federal Register on June 11, 1992.
  2. Revision of laws and regulations impeding metric conversion. In 1991, the work group tackled maximum speed limit regulations and standard design criteria. However, exactly how and when to convert speed limit and other highway signs to metric has yet to be decided and implemented. In the meantime, FHWA's chief legal counsel has advised that it's permissible to convert "55 mph" to "90 km/h" because these two values are "functionally equivalent." This means that, if it's ultimately decided to convert signs to metric, no legislation to modify the 55-mph speed limit will be required.
  3. Conversion of all FHWA manuals, documents, and publications to metric. Effective Oct. 1, 1993, to the maximum extent practicable, all FHWA reports and correspondence were to use only metric. FHWA program and policy offices actively support this objective. Many have issued stringent memoranda to enforce this deadline.
  4. Conversion of all FHWA data collection and reporting. As of Oct. 1, 1994, new data submitted to FHWA's data collection and reporting systems, such as the Highway Performance Monitoring System and the National Bridge Inventory System, were to be in metric. At the discretion of individual program offices, past data collection and reporting were to be converted to metric.
  5. Conversion of construction contracts, plans, and specifications. By fiscal year 1997, newly authorized federal lands, highway, and federal-aid construction contracts must be expressed in metric units only. After Sept. 30, 1996, all plans and specifications for construction projects are to be in metric units only. (For those cases where it would be counterproductive to convert to metric, the work group has issued guidance about requesting and justifying exceptions.)


FHWA metric cube


Metric Training Is Aimed at Both Psychological and Technical Problems

The National Highway Institute course, "Metric (SI) Training for Highway Agencies," has been made available for use by state and local governments as well as the private sector. A first session, recommended for all employees, covers general metric information and the correct use of terms. A second session is designed for technical personnel and geared to highway disciplines such as planning, environment, design, materials, and construction, with breakout groups to focus on specific problems and applications.

FHWA and the American Association of State Highway and Transportation Officials (AASHTO) cosponsor another major education effort -- the annual National Metric Conference -- to allow nationwide sharing of metric implementation ideas and techniques. In the winter of 1994, more than 200 people attended the first such conference at Research Triangle Park in North Carolina. Participants included metric coordinators from state highway agencies and FHWA field offices; experts and consultants; and representatives from federal government agencies, academia, the construction industry, and various engineering and transportation-related associations. A second National Metric Conference was held February 1995 in Phoenix.

"Hard" Versus "Soft" Conversion

The federal government makes a distinction between "hard" and "soft" conversions to the metric system. A soft conversion is a direct mathematical conversion from a U.S. measurement to its metric equivalent e.g., from 180 pounds to 81.65 kilograms. A hard conversion is the creation of a new, rounded, rationalized number that is easy to work with and easy to remember.

FHWA encourages the use of hard conversion as much as practicable. Where hard conversions have not been established, however, state highway agencies should use soft conversions. The bottom line is that a project should not be delayed simply because some hard conversions have not been developed yet.

Several agencies, including FHWA, have adopted the American Society for Testing and Materials (ASTM) manual E380 as the standard for making metric conversions. An excellent reference is the Metric Guide for Federal Construction published by the National Institute of Building Sciences.

Efforts are not standing still between conferences. The ideas generated in conference are being put into action. Other FHWA metric training and education efforts include the following:

  1. FHWA has developed and distributed more than 150,000 metric/U.S. measurement conversion slide rules to its field offices, state highway agencies, technology transfer centers, and other appropriate offices.
  2. Two of FHWA's regional offices have developed computer conversion programs for general use. These programs have been distributed agencywide and are available on FHWA's electronic bulletin board.
  3. FHWA developed and has made available a computer software program that can be used within WordPerfect to convert U.S. measurement units to metric units.
  4. FHWA has developed and made available a metric poster and a metric cube (a small box with metric conversion information on all six sides).


DOT metric tape measure.


Metric Highway Signs?

There is as yet no requirement in FHWA's metric conversion plan to change the legends on highway signs to metric units. However, three approaches to this task are being considered: (1) conversion through routine maintenance, (2) "quick" conversion, and (3) transitional conversion with dual metric and U.S. measurement units. To gauge public attitudes toward these approaches, FHWA solicited public comments in a notice to the Federal Register. The 1994 Highway Appropriations Act contained a provision prohibiting the use of federal-aid funds for the placement of metric signs during FY 1994.

Several bills have been introduced this year in Congress to extend the prohibition against metric signing. For example, a recently passed House bill to approve the National Highway System contains a provision that would prohibit FHWA from requiring states to convert highway signs to metric before Sept. 30, 1997.

In the interim, FHWA will continue to prepare for an orderly conversion of highway sign legends to metric units and will also help any state that wants to develop plans for converting its highway sign legends to metric units.

Action at the State Level

AASHTO has been highly supportive of the metric conversion goal. Its Standing Committee on Highways' Task Force on Metrication is coordinating AASHTO's conversion efforts. These include developing a handbook, AASHTO Guide to Metric Conversion.

Additionally, an AASHTO clearinghouse has been established to monitor and inform state highway agencies on metrication issues. AASHTO has contracted with the Texas Transportation Institute to operate this clearinghouse, which collects and shares information from state highway agencies on their experiences in converting to the metric system. The information will be communicated electronically to the states through AASHTO's Value-Added Network (AASHTOVan).

Metric information contained on AASHTOVan will include a periodic newsletter updating important metric issues, quarterly conversion survey results, an interactive forum for metrication issues, selected bibliographies, a directory of metrication contracts, and a calendar of metrication events.

State departments of transportation are also making vital contributions. By the end of 1994, 43 state DOTs were designing all their new projects in metric only. Forty state DOTs are planning to implement pilot projects before the Sept. 30, 1996, target date and are converting their standard specifications for highway construction to metric.

The Long Wait for Metric Is Nearly Over

Both Congress and the executive branch are firmly behind metric conversion. Private sector support is also much stronger this time around. In fact, about 30 percent of American products -- including farm equipment, automobiles, drugs, medicines, and beverages -- have already "gone metric."

With regard to some of the psychological and technical difficulties of implementing the metric system in highway construction, a contractor responding to FHWA's Notice of Proposed Policy statement in the Federal Register put the case well:

"Having used the metric system previously, I can assure you that anyone, even if they are dragged kicking and screaming into it, will find it vastly superior to the ancient English system. One foot is within 3/16ths of an inch of 30 centimeters. My slipform paving machines will not know the difference, nor will my crusher know whether it's crushing centimeters or inches. A 1.5-inch screen is close to 4 centimeters and so forth. In figuring volumes of concrete, the tedious (mathematical calculations to convert) fraction to decimal inches, then to decimal feet, then dividing by the cumbersome 27 to get cubic yards is replaced by straight decimal multiplication. Within tolerances, a 10-yard mixer holds 7.5 cubic meters."

A lot of conversion has already taken place. Electronic equipment can do metric at the push of a button or with very minor programming. Many nuts and bolts and other machinery parts are already metric. Most workmen's tapes include metric as well as foot/inch. We buy bottled soft drinks and liquor by the liter, and nobody complains. When people think of a meter as simply a unit of measure that is broken into handy decimal divisions instead of as 39.37 inches, the mystery goes away.

FHWA, AASHTO, the states, and the private sector are all working hard to dispel the mystery. Time and practice will do the rest. Eventually, kilometers per hour, square meters, kilometers per liter, and the rest will become as natural and automatic as miles per hour, square feet, and miles per gallon are today. It was revolutionary in 1793. Today, it's just common sense.

The History of Metrication in the United States

1800 -- The U.S. Coast Guard and Geodetic Survey (the government's surveying and map-making agency) adopt meter and kilogram standards from France.

1866 -- Congress authorizes use of the metric system in the United States and supplies each state with a set of standard metric weights and measures.

1875 -- The United States is one of the original 17 nations to sign the Treaty of the Meter. This agreement establishes the International Bureau of Weights and Measures to provide worldwide standards.

1893 -- The United States adopts metric measurement standards for length and mass. The foot, pound, quart, etc., have been defined in relation to the meter and kilogram ever since.

1960 -- The same nations that signed the Treaty of the Meter approve a modernized version of the metric system, called the International System of Units (SI).

1965 -- Great Britain, as a condition for becoming a member of the European Common Market, begins transition to the metric system in its trade and commerce. This move creates a sense of urgency in the United States to convert as well.</

1968 -- Congress passes the Metric Study Act of 1968 to study the feasibility of adopting SI. The ensuing report recommends that the United States convert to predominant use of the metric system over a 10-year period.

1975 -- Congress passes the Metric Conversion Act to plan and coordinate the transition. The U.S. Metric Board is established and voluntary conversion begins.

1981 -- The Metric Board reports to Congress that it lacks the authority to bring about nationwide conversion.

1982 -- The Metric Board is abolished, increasing doubts about the U.S. commitment to metrication.

1988 -- Congress includes strong, new incentives for U.S. industrial metrication in the Omnibus Trade and Competitiveness Act of 1988. This legislation designates metric as the "preferred system of weights and measures for U.S. trade and commerce." It also requires that, by the end of 1992, all federal and federal-aid agencies use the system in their procurements, grants, and other business activities.

David Smith, Ph.D., is freelance technical writer on-contract to Public Roads. He is also president of AMANUENSIS Inc., a creative writing agency specializing in advertising and marketing copy for technology providers, in McLean, Va. He has more than 12 years of advertising agency experience, including 10 years as a vice president and account manager for one of the largest agencies in the Washington, D.C., area. He is a graduate of Cambridge University and the University of Kent at Canterbury, England, with degrees in international relations and diplomatic history.