a sign saying "4/10 Mi" is not easily converted to feet or yards, at least its easier to comprehend than "2/5 Mi", which has to be converted to a base-ten fraction to be calculated with your trip odometer (which does display tenths in decimal form, unlike my standard odometer which has no tenths display at all). As long as trip computers have decimals and not fractions, I see no reason to reduce fractions on signs into a form that has to be expanded to be understood.

I would much prefer an approximation of "4/10 mi" instead of 2000 feet or something close, which means nothing to me at 60 mph.

1 mile = 5280 feet = ~1600 meters.

Rounding purposes, especially at highway speeds, 5000 feet is a close approximation for 1 mile. Every tenth of a mile is (28 feet more than) 500 feet

Signing distances in footage multiples of 500 is practically equivalent to tenths of a mile

.4 mi = 4/10 mi = ~2000 feet. All the same

Don’t know what states exactly, but driving around, especially construction zones, I tend to notice signs in 500 foot multiples for distance...500 feet, 1000 feet, etc. Not 1/10, 2/10s, etc

Now in meter multiples of 160 would be fun, but it is still functionally equivalent to tenths of a mile