California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

uses a postmile highway location marker system on all of its

state highway A state highway, state road, or state route (and the equivalent provincial highway, provincial road, or provincial route) is usually a road that is either Route number, numbered or maintained by a sub-national state or province. A road numbered ...

s, including

U.S. Route The United States Numbered Highway System (often called U.S. Routes or U.S. Highways) is an integrated network of roads and highways numbered within a nationwide grid in the contiguous United States. As the designation and numbering of these h ...

s and

Interstate Highway The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, or the Eisenhower Interstate System, is a network of controlled-access highways that forms part of the National Hi ...

s. The postmile markers indicate the distance a route travels through individual counties, as opposed to

milepost A milestone is a numbered marker placed on a route such as a road, railway, railway line, canal or border, boundary. They can indicate the distance to towns, cities, and other places or landmarks like Mileage sign, mileage signs; or they c ...

s that indicate the distance traveled through a state. The postmile system is the only route reference system used by the

California Department of Transportation The California Department of Transportation (Caltrans) is an Executive (government), executive department of the U.S. state of California. The department is part of the Government of California#State agencies, cabinet-level California State Tran ...

(Caltrans). The system was operative by 1966. California was the last state in the country to adopt mile markers, and exit numbers were not implemented until 2002. The state started the Cal-NExUS program in 2002, which would create a uniform exit numbering system for freeways. 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 Kern County is a county (United States), county located in the U.S. state of California. As of the 2020 United States census, 2020 census, the population was 909,235. Its county seat is Bakersfield, California, Bakersfield. Kern County compris ...

, and State Route 180 in

Fresno Fresno (; ) is a city in the San Joaquin Valley of California, United States. It is the county seat of Fresno County, California, Fresno County and the largest city in the greater Central Valley (California), Central Valley region. It covers a ...

. Caltrans has not decided if the mile marker program will be expanded to all rural freeways.Cal-NexUS FAQ
Caltrans. Accessed: 10-24-2009. Regardless, Caltrans will still use and maintain the postmile system on all freeways.

Format

A postmile marker is placed along the state highway. Each marker is stenciled with the route, county, and postmile at that location.

Current formats

Bridge

One of the common formats for postmiles are located on a freeway on bridges over cross streets. According to Caltrans, it displays the name of the bridge, the county and route number, and the postmile. The postmile is often painted onto the piers and/or abutments of bridges and overpasses.

Postmile markers

These are the white metal paddle markers placed at one-mile (1.6 km) intervals, with additional markers placed at significant features along the highway such as bridges and overpasses, junctions, or culverts. The markers are roughly the same size as a standard milepost used elsewhere, but they are white with black text. These markers also indicate turnouts and cross streets ahead.

Callbox

Postmiles are also shown on callboxes. A blue placard is mounted on each of the state's callboxes: the top shows which county the callbox is in, and the bottom shows the 2-letter county abbreviation along with the route number and the location's postmile (in tenths of miles). Postmiles on callboxes are approximate due to a convention that all callboxes on the northbound or eastbound side of a divided roadway are assigned even numbers while all those on the southbound or westbound side are assigned odd numbers, even though the call boxes are often located directly across from one another.

County prefixes

Alphabetic prefixes on postmile markers and bridges differ from callbox prefixes because the callbox system is maintained by each county, while

Caltrans The California Department of Transportation (Caltrans) is an Executive (government), executive department of the U.S. state of California. The department is part of the Government of California#State agencies, cabinet-level California State Tran ...

maintains postmile markers and bridge signs. The following table lists postmile and callbox prefixes by county.

Official postmile definitions

Listed in miles, postmile values usually increase from south to north or west to east depending upon the general direction the route follows within the state. The postmile values increase from the beginning of a route within a county to the next county line. The postmile values start over again at each county line. Enforcement officers, maintenance forces and others use the postmile markers in the field to locate specific incidents or features with reference to the postmile system. On some stretches of road, the following prefixes may precede the mileage on a postmile marker: A postmile may also include a milepost equation.

Similar reference markers in other jurisdictions

Sonoma County Sonoma County ( ) is a county located in the U.S. state of California. As of the 2020 United States census, its population was 488,863. Its seat of government and largest city is Santa Rosa. Sonoma County comprises the Santa Rosa-Petaluma ...

uses a postmile system on its county roads, but the numbering usually starts at 10.00 rather than at a zero point.

Los Angeles County Los Angeles County, officially the County of Los Angeles and sometimes abbreviated as LA County, is the most populous county in the United States, with 9,663,345 residents estimated in 2023. Its population is greater than that of 40 individua ...

uses a postmile system similar to the state’s, but their postmile markers contain a red bar on its top The states of

Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...

and

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

use reference markers very similar to California's postmile markers. Like California, these two states record mileages through individual counties in their respective route logs. Ohio's system is nearly identical to California's with its reference markers listing the route number, 3-letter county abbreviation, and mileage through the county. The Nevada system is also similar, utilizing 2-letter county abbreviations. However, Ohio uses standard mileposts in addition to reference markers on freeways, while Nevada uses standard mileposts in conjunction with postmile panels on Interstate highways only. Also, all non-

Interstate The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, or the Eisenhower Interstate System, is a network of controlled-access highways that forms part of the National H ...

s in

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

and

Kentucky Kentucky (, ), officially the Commonwealth of Kentucky, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Illinois, Indiana, and Ohio to the north, West Virginia to the ...

have markers showing mileage from the western or southern border of the county.

References

External links

*Caltran
Postmile Services
{{DEFAULTSORT:California Postmile Postmile Milestones Road signs in the United States