As my students know, I like metric, so I am saddened by this in the NY Times: Dropping Kilometers From Highway's Signs Divides Arizona
Distance along I-19 is measured in kilometers, just as it is in Mexico. That means highway markers advise that there are three kilometers until the next gas station, four until the next rest stop, seven until the next desert town.
But the distinctive signs' days may be, well, numbered.
The Arizona Department of Transportation says the 400 signs along the I-19's 100 kilometers are too old and need to be replaced. The new signs, officials say, would be like all the others in the state and would indicate distance in miles. Exit numbers would be reconfigured as well.
I have nothing against dual units (putting miles below km to help the British tourists out), but a full-scale conversion seems foolish and expensive, and why need exits be changed, km gives you the opportunity for more integer exit signs, while with miles, you might need an a, b, c suffix to the exit if there are a cluster of off-ramps.