Interstate 66 (west) - Numbering Considerations

Numbering Considerations

A completed I-66 would not be in strict compliance with AASHTO Interstate Highway System numbering standards, since most of it would actually run south of existing I-64. A similar condition exists where I-75 and I-85 cross over at Atlanta, Georgia, so it is not without precedent. I-99 in Pennsylvania is also out of sequence, though its designation was written into law by its Congressional sponsor, Bud Shuster, not designated by AASHTO. However, I-64 doesn't yet exist west of St. Louis Metro, so west of around Poplar Bluff, this section of I-66 would comply with AASHTO, since the western terminus of I-64 is at this longitude.

Another concern is that the proposed route of I-66 in Missouri and Kansas would cross the former path of historic U.S. Route 66. However, as the US route has been decommissioned, there would be no official route numbering conflicts. Proposed expansions of other Interstate corridors are expected to have intersections with similarly numbered active US routes, such as the future intersection of Interstate 69 and U.S. Route 69 in Texas, and Interstate 74 and US 74 in North Carolina.