DESIGN MEMORANDUM NO. 11-98

TO:                                           Chief District Engineers
                                                  Active Consultants
                                                  Active Consultants

FROM:                                     John B. Sacksteder, P.E.
                                                  Director, Division of Highway Design

DATE:                                      November 4, 1998

SUBJECT:                               English Conversion

As most of you are aware, it was recently announced that effective on October 1, 1998, Kentucky would move away from the metric production of plans and return to English only. In Secretary Codell’s September 30, 1998, memo on the subject, he states, "This Cabinet will continue to use metric units for projects in the development phase at present, and all current construction contracts will be brought to conclusion in the system as designed. All new projects commenced on or after October 1, 1998, will be in English units. It is realized that some years will be required to be entirely reverted to English."

Based on the above, the following guidelines should be used to determine which projects should be converted to English:

1. All new project starts shall be in English. Projects that currently have photogrammetry requests pending will be flown and delivered in English units.
   
   
2. Projects that have not yet had Preliminary Line and Grade Inspection and would not have their schedules impacted shall be converted.
   
   
3. Projects that are in Phase I Design and have already had a Preliminary Line and Grade Inspection, but are being delayed by pending Environmental Approval or by future funding availability, may be converted. The Project Team should carefully investigate these projects to assure that the conversion would not cause problems with the environmental document; i.e., detailed information on stationing or quantities would require a significant re-write of the environmental document requiring a delay in its completion.
   
   
4. Projects in Final Design that have letting dates beyond 2004 (non-Six Year Plan Projects) may be converted, as long as the conversion will not have any delays on other aspects of the project such as right-of-way or utility activities.
   
   
5. Other projects may be considered on a case by case basis, as long as no delays will be created by the conversion.

The obvious emphasis in all of the cases listed above is that no delays in the project are to occur as a result of the conversion from Metric to English. If the Project Team believes that a delay may be required to accomplish the conversion, then the project must continue in Metric terms. Tips for the conversion from Metric to English will hopefully be on the Department’s Division of Highway Design web page by November 15. The CADD staff has been working diligently in the development of a process for the conversion of the projects. They now believe that the conversion of photogrammetry, fieldwork, and basic design geometry can be accomplished in as little as a day’s time for a moderately sized project. How this can be accomplished will be detailed on the web site. Our web site can be accessed at www.kytc.state.ky.us/design/design.htm.

Our photogrammetric consultants can translate completed photogrammetry that has not yet been utilized for design. However, because of demands on their time to meet current schedules, the use of this conversion method should be limited. If the photogrammetric firms are requested to convert very many of the formerly completed presentations, it will obviously hamper their capability to meet the current schedules and provide any prioritized conversions.

The cost of converting from Metric to English should also be minimized. When converting plans that have already been detailed to some degree, it is suggested that the soft conversion of templates in the plans and cross-sections be permitted to lessen the amount of work required for the conversion. It is felt that the degree of tolerance for calculation of earthwork quantities, etc., will not generally be compromised by the soft representation of template lines. Similarly, the soft conversion of the cross-sectional elements should also be accepted where the cross-sections have been previously developed; i.e., permit cross-sections at non 50’ intervals to accommodate the current 20 m intervals. Typical sections will be provided to reflect the proper lane, shoulder, and ditch widths. If felt necessary, a note may be added to the plans and cross-sections indicating the use of soft conversion of Metric plans. If the Project Team believes a more detailed conversion would be required because of the number of lanes, quantity of earthwork, or other such factors involved, then the choice should likely be to retain the project in Metric form. Recommendations to convert such projects to English should be discussed with the Director of Highway Design prior to any conversion occurring.

English geometric standards are currently being updated and will be available later this year. Until such time that new standards are available, designers are cautioned that the old English standards do not necessarily meet all current criteria. The continued use of the current Metric standards as the guide for criteria is recommended until the English update is completed. Obviously we will be using 12’ lanes, etc., as the English standard. However, some changes that occurred with metrication will continue. For example, we will continue the use of per cent representation of slopes rather than foot per foot; i.e., 2% pavement slope rather than .0208 `/`. Curves will also remain in feet of radii. The degree of curve is deemed to be an archaic representation that is not reflected in current national guidance. Side slopes will return to their former English designation; i.e., 4:1 rather than 1:4.

More guidance on all of these matters and more will be forthcoming shortly.

JBS:jad