California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

uses a postmile

highway location marker A highway location marker is the modern-day equivalent of a milestone. Unlike traditional milestones, however, which (as their name suggests) were originally carved from stone and sited at one-mile intervals, modern highway location markers are m ...

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 ''numbered'' or ''maintained'' by a sub-national state or province. A road numbered by a ...

s, including U.S. Routes and

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

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

milestone A milestone is a numbered marker placed on a route such as a road, railway line, canal or boundary. They can indicate the distance to towns, cities, and other places or landmarks; or they can give their position on the route relative to so ...

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 department of the U.S. state of California. The department is part of the cabinet-level California State Transportation Agency (CalSTA). Caltrans is headquartered in Sacrame ...

(Caltrans). California was the last state in the country to adopt mile markers, and

exit numbers An exit number is a number assigned to a road junction, usually an exit from a freeway. It is usually marked on the same sign as the destinations of the exit. In some countries, such as the United States, it is also marked on a sign in the go ...

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 located in the U.S. state of California. As of the 2020 census, the population was 909,235. Its county seat is Bakersfield. Kern County comprises the Bakersfield, California, Metropolitan statistical area. The county sp ...

, and State Route 180 in

Fresno Fresno () is a major city in the San Joaquin Valley of California, United States. It is the county seat of Fresno County and the largest city in the greater Central Valley region. It covers about and had a population of 542,107 in 2020, maki ...

. 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

callbox A call box or callbox is a (usually metal) box containing a special-purpose direct line telephone or other telecommunications device which has been used by various industries and institutions as a way for employees or clients at a remote loca ...

es. 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 A milepost equation, milepoint equation, or postmile equation is a place where mileposts on a linear feature, such as a highway or rail line, fail to increase normally, usually due to realignment or changes in planned alignment. In order to make mi ...

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 county seat and largest city is Santa Rosa. It is to the north of Marin County and the south of Mendocino ...

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 L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is the ...

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 U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

and

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

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, is a network of controlled-access highways that forms part of the National Highway System in the United States. Th ...

s in

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...

and

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

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