METRICATION FOR LOCAL AGENCIES By WILLIAM T. SUNLEY, Engineer of Local Roads and Streets

As many of you are aware, all federally funded highway and bridge projects with bid openings after September 30, 1996 must utilize the metric system. It will also be necessary to change from the English system to the metric system for non-federally funded projects because of the difficulties that would be encountered in trying to maintain a dual system. The Department has established a task force to develop and oversee IDOT's conversion to metrics.

The American Association of State Highway and Transportation Officials (AASHTO) standards have been selected by the Federal Highway Administration (FHWA) as the basis for conversion to the metric system. While not all of the standards have been established yet, most of the basic conversions have been finalized.

Initially, many of the current dimensions and values will be converted to "soft" metrics; that is, no physical changes will be required and conversion will be to the nearest acceptable value. However, it is often undesirable to use soft conversion because the metric equivalent may be cumbersome to work with. For example, the soft conversion for a standard 12 foot wide traffic lane is 3.658 meters. The hard conversion is 3.6 meters, which is more convenient to work with and is still within acceptable limits from an operations standpoint. Some soft metric conversions will continue to be used while others will be changed to "hard" metric values which will require a physical change in the size of some features or objects to convenient metric values. While the FHWA prefers hard metric conversion it is not mandated and therefore, soft metric conversion is acceptable.

The Standard Specifications for Road and Bridge Construction are in the process of being updated. The edition that will be published in the fall of 1993 will show both the current English system value and the metric equivalent. Prior to the conversion deadline, the Standard Specifications will be updated once more and that edition will contain only metric values. Interim special provisions, recurring special provisions and Local Roads special provisions will be converted to metrics on approximately the same time frame.

The Department is working with representatives of the consulting engineers' organizations to identify areas of concern to both parties. There will be a transition period when plans for some projects are being developed in English units while other, newer projects will be designed using metric units.

An issue of major concern to the task force is the capability of the construction industry and their suppliers to adapt their operations to the changes in units of measurement. It will require a considerable amount of cooperation between all parties to accomplish the changeover. Producers and suppliers will be required to redo their measuring and weighing equipment in order to provide specified materials within acceptable tolerances. Allowable capacities for various pieces of equipment will need to be re-computed. Testing equipment must be replaced or recalibrated to accommodate the metric units of measurement. Contractor's organizations and supplier's organizations are well represented on the metric conversion task force and their comments are considered a vital part of the decision making process.

During the changeover period, the Department will provide guidance to local agencies, their consultants and their contractors. Contract administration will need to be conducted in dual units for several years beyond 1996 until all English unit contracts have been completed. The Bureau of Local Roads and Streets will issue periodic updates on the task force activities. •

October 1993 / Illinois Municipal Review / Page 7