MileCheckWhat do the small green signs every tenth of a mile mean?
They are mile markers with a decimal. The federal sign manual calls them intermediate reference location signs. One that reads 152.4 is four tenths of a mile past mile 152.
What the manual says
The federal Manual on Uniform Traffic Control Devices (MUTCD, 11th edition) covers both kinds. Plain reference location signs show the whole mile. Intermediate ones add a decimal and go up at a regular spacing, such as every tenth of a mile (checked November 5, 2026).
Enhanced versions add the route shield and direction to the sign. Those are taller and easier to read from a car.
Where you see them
Mostly on busy urban freeways, where a tenth of a mile can be the difference between two interchanges. Many rural roads only have whole-mile signs.
Using them to report a location
Read the number as it is, such as "northbound I-5 at mile 152.4." It narrows the spot to about 500 feet.
The MileCheck app shows your position to one decimal on roads that only have whole-mile signs. It places you between the two nearest recorded markers.
See your mile marker as you drive
MileCheck shows your nearest mile marker, the highway and your direction. Premium adds live state DOT feeds for the road ahead and the map, with a 2-week free trial. It runs on CarPlay and Android Auto.
Questions, answered
Are they every tenth of a mile everywhere?
No. The manual allows a tenth of a mile or another regular spacing, and each state decides where to put them.
Why do some have a route shield on top?
Those are enhanced reference location signs. They show the route and direction above the number.