The majority of road signs featuring distances along Interstate 19 are in metric units. Interstate 19 runs from the U.S.-Mexican border at Nogales, Arizona and Nogales, Sonora to just southeast of Tucson at Interstate 10.

Contrary to folklore, the signs are not metric because the road goes to Mexico. Actually, Interstate 19 was built when the United States was to convert to metric during the Carter Administration. That plan was abandoned when Reaganomics swooped in, but the metric signs, including interchange numbers related to their kilometer-post, stayed in place. The signs were last replaced in 1999, again with metric units. In 2010 ADOT started replacing the signs at the northern end of the freeway with customary units, but local opposition to the conversion stalled that project. Businesses in particular didn’t want to see the interchanges renumbered because that would mean changing directions to their business. So, the metric signs still stand and the exit numbers are based on the number of kilometers from the southern end of the freeway.

Because of their age, some signs have been replaced in the last year or two and they use the same exit number and “km” instead of “miles” for distance. When you jump onto I-19 from I-10 in Tucson you’ll see “Interstate 19 uses metric signs”. Speed limits are still in English units (55/65/75).

I love the metric signs on Interstate 19 and I love the old button-copy legend (the letters with the reflectors in them). Arizona and Ohio were the last two states to use this type of lettering on their signs and I’ve always found them to be more professional and sturdier looking.

I remember the optimism surrounding the plans to switch to metric when I was in elementary school. In fact, when we learned units of measure as part of our elementary school education, it was all metric based. New York State was progressive and all that. To this day I have no idea how many quarts are in a pound or how many pints are in a hectare. Don’t even get me started on chains and rods, when I went to college for Civil Engineering, roads were still being designed to metric units. NYSDOT switched back to English units right after I was in college in the late 2000s.

It’s a shame the United States can’t embrace the metric system because of Yankee Doodle Yacky and God Bless America and all that. The metric system makes much more logical sense.

But logical sense has never been a strong point of American society.