Metric system: there is or was one 60 mile stretch of road between Tucson and Nogales Mexico that was signed in metric. (apparently the mexicans are supposed not to understand MPH even though they drive American cars.)
The decision was made this year to take down those signs and replace them with MPH signs.

Haven't been to Nogales in years, since when the cartels start shooting at each other, some bullets may have "to whom it may concern"