The National Academies

NCHRP 20-40 [Completed]

Conversion of AASHTO Publications to Metric Units

  Project Data
Funds: $1,208,581 (Phases I and II)
Research Agency: Texas A & M
Principal Investigator: Byron C. Blaschke
Effective Date: 11/10/1994
Completion Date: 5/10/1999

This project accomplished the "hard" conversion of 16 major AASHTO publications to the metric (SI) system of measurement units in a form suitable for publication. Hard conversion is a process in which an inch-pound standard size is replaced with an accepted metric standard size for a particular purpose. The project also maintained and operated the Internet-based AASHTO Metrication Clearinghouse from 1995 to 1997.

The FHWA Metric Conversion Plan, approved by the Secretary of Transportation in October 1991, mandated that all plans, specifications, and estimates must be in metric units for federal aid projects with project agreements executed after October 1, 1996. To bring its highway development programs into compliance with the October 1996 target date, AASHTO and its member departments initiated a series of efforts to convert standards, guidelines, specifications, pay units, and numerous other items to the metric measurement system. This project was undertaken to ensure a timely, comprehensive, and coordinated effort to convert key AASHTO documents, including specifications, standards, manuals, and guidelines.

Metric versions of the 16 selected documents were delivered to AASHTO in reproducible format during the period July 1996 through January 1999. Operation responsibility for the AASHTO Metric Clearinghouse on the Internet was transferred to AASHTO on January 1, 1998. A brief final report of the project was published as NCHRP Research Results Digest 240.

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