See below:
http://en.wikipedia.org/wiki/Interstate_19
“Interstate 19 is unique among US Interstates, because signed distances are given in meters (hundreds or thousands as distance-to-exit indications) or kilometers (as distance-to-destination indications), and not miles. However, the speed limit signs give speeds in miles-per-hour. According to the Arizona Department of Transportation (ADOT), metric signs were originally placed because of the push toward the metric system in the United States at the time of the original construction of the highway.”
< snip >
“Citing motorist confusion arising from the metric signs on I-19, Arizona DOT’s Tucson district announced that new signs on I-19 would use United States customary units. To avoid the cost of replacing the metric signs all at once, signs would be replaced in specific areas of the freeway during construction projects in those areas.[7] New signs were put into place between Exit 99 (Ajo Way) and Exit 101 (Interstate 10) in 2004 after the completion of the new Interstate 10–Interstate 19 interchange.”
W/ just a few redneck friends, and just a few beers, those km signs would all disappear.