California uses a postmile highway location marker system on all of its state highways, including U.S. Routes and Interstate Highways. The postmile markers indicate the distance a route travels through individual counties, as opposed to mileposts that indicate the distance traveled through a state. The postmile system is the only route reference system used by the California Department of Transportation (Caltrans). The system was operative by 1966.[1]
California was the last state in the country to adopt mile markers, and exit numbers were not implemented until 2002.[2] The state started the Cal-NExUS program in 2002, which would create a uniform exit numbering system for freeways.[3] Included was a pilot program for the placing of mile markers along rural freeways. Currently, three freeway segments are a part of the experimental program: the Route 14 Freeway, the Route 58 Freeway in Kern County, and State Route 180 in Fresno. Caltrans has not decided if the mile marker program will be expanded to all rural freeways.[4] Regardless, Caltrans will still use and maintain the postmile system on all freeways.[4]