Union Pacific Control Points
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This page was last updated on September 28, 2026.
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Overview
A Control Point (abbreviated as CP, or C.P.) is a designated location on a railroad that is controlled by a remote operator, such as an electric switch for a siding, a crossover between two parallel tracks, or a crossing of two or more tracks. Control Points are displayed on trackside signs. Union Pacific began using the term Control Point (or Controlled Point) in late 1979 when a bulletin was issued by the railroad's engineering department.
A control point (CP) operates at intersecting or diverging track locations—such as the ends of passing sidings or track crossovers—and is managed remotely by a dispatcher or a control operator. These points use electric track switches alongside a trackside instrument house (or smaller relay cabinet) that houses necessary power supplies, batteries, chargers, and relays. Modern control points also require additional space for Positive Train Control (PTC) radios, radio interfaces, and fiber-optic equipment. Historically, "interlocking" referred specifically to a junction between two different rail lines controlled remotely via telephone, but today the terms control point and interlocking are used interchangeably.
On Union Pacific, "Control Point" was first (in 1979) abbreviated on standard drawings for trackside signs as "C.P." Later simplified on trackside signs as "CP".
The Rules
(The term "controlled point" is generally a term used in government documentation, with the railroads and railroad supply companies more commonly using the term "control point.")
Control Points are regulated and governed by the Federal Railroad Administration, under its "Rules and Regulations Governing Railroad Signal and Train Control Systems" Part 236. (49 CFR Part 236)
According to DOT/FRA Title 49 of the Code of Federal Regulations (49 CFR Part 214):
- Controlled point - A location where signals and/or other functions of a traffic control system are controlled from the control machine.
- Controlled track - Track upon which the railroad's operating rules require that all movements of trains must be authorized by a train dispatcher or a control operator.
- Control operator - A railroad employee in charge of a remotely controlled switch or derail, an interlocking, or a controlled point, or a segment of controlled track.
In the ICC and later FRA documents, "Controlled point" means a location where signals and/or other functions of a traffic control system are controlled from the control machine.
The earliest published references to "controlled point" in the U. S. government's Federal Register appear in March 1950, published by the Interstate Commerce Commission (ICC) — the agency that regulated railroad safety before the Federal Railroad Administration (FRA) was created in 1966.
On June 29, 1950, the Interstate Commerce Commission issued its major overhaul of signal and train control regulations under its Ex Parte No. 171 document. These rules established standardized federal regulations governing Centralized Traffic Control (CTC) systems, codified in Title 49 as Part 136 (49 CFR 136) (which the FRA later renumbered to 49 CFR Part 236 in 1968).
The phrase "controlled point" first appeared in the June 29, 1950 updated order for signal systems, in changes to 49 CFR Part 136.403, "Signals at controlled point." and 49 CFR Part 136.404, "Signals at adjacent control points."
There were updates in 1966 and again in 1984, but they referred back to the ICC's Ex Parte 171 signal regulations in Part 136, dating from 1950. The ICC rules carried over when the FRA assumed jurisdiction in 1966, and were made formal when the FRA issued its own deddicated definition section.
Conrail and Amtrak may have been the first to formally adopt the use of "control point" (C.P., or CP) in 1976 when they eliminated tower names and replaced names with "CP" prefixes in employee timetables. In 1978, the Federal Railroad Administration made a rule concerning worker track-safety protection within "controlled point limits" (49 CFR Section 218). Union Pacific adopted its own version of the controlled point terminology in 1979.
Research has not yet found the reason most railroads held off using the "controlled point" or "control point" phrase in their own operations and documents until the mid- and late-1970s. However, comments by current and retired railroad industry personnel suggest that by the late 1970s, the railroads decided to address the confusion between interlocking operating rules and CTC operating rules, which were not always the same. In 1984, as the General Code of Operating Rules (GCOR) was about to be adopted by numerous western railroads, the FRA adopted language in its own rules that addressed variations between operating rules through interlockings, and operating rules across territory under Centralized Traffic Control.
Today, all the major Western and Midwest railroads use the “General Code of Operating Rules” (GCOR). Many northeastern railroads, including Amtrak’s Northeast Corridor, use the Northeast Operating Rules Advisory Committee (NORAC) rulebook. Norfolk Southern, CSX, Florida East Coast, Grand Trunk, Illinois Central, KCS, and some smaller lines each have their own books. One rulebook covers all lines in Canada.
(Read more about the Rule Books as part of Train Control)
Mile Posts
As an overall statement for present-day operations and the previous 20 years, all mile posts on Union Pacific are numbered from major terminals. Eastward from Los Angeles on former UP lines. Eastward from Oakland on former SP lines, and former WP lines. Westward from Chicago on former C&NW lines. Westward from Council Bluffs on former UP lines. Points on former MP and MKT routes are a mix of several terminals.
Although minor variations exist in the mile post numbers over time, they have generally remained the same. Many mile post numbers were taken from the center of the point of a historical depot, or from the center of a station's siding. Over time, variations in station mile post numbers came mainly due to sidings being lengthened, and the center of the siding moving to reflect the new length. Other variations exist due to the line being re-surveyed.
As mentioned below in the original 1979 order, "CP" numbers were assigned according to the nearest mile post.
The Chief Engineer's Bulletin
December 10, 1979
Union Pacific changed its way of designating signal and switch locations, adding "C. P." to the mile post designations, denoting a "Controlled Point" (later just Control Point) (UPRR Office of Chief Engineer Instruction Bulletin, dated December 10, 1979)
To: Division Engineers and all Supervisors and Foremen in the Track and Signal Department.
Subject: "Controlled Point" Locations in CTC Territory.
In order to effectively identify signal and/or switch locations in CTC territory that are controlled by the train dispatcher, selected locations will be designated as "Controlled Points" with an assigned "Controlled Point Number" which will correspond with the milepost nearest the "Controlled Point."
"Controlled Point" and "Controlled Point Number" are defined as follows:
Controlled Point (CP): A location where signals and/or switches of a CTC System are controlled by train dispatcher or control operator.
Controlled Point Number: A number, assigned to a controlled point, which designates the location of the controlled point (to the nearest milepost). When necessary to contact train dispatcher or control operator, employees must use controlled point number to identify their location.
Controlled point numbers will be placed on the instrument house at each designated controlled point in accordance with Drawing C.S. 17-B dated July 16, 1979 which is included as part of this bulletin. At outlying locations where a station name has not been assigned the Type "B" sign depicting only the controlled point number will be installed; however, at locations where a station name has been assigned the Type "A" sign will be installed, which depicts both the station name and the controlled point number. The "Controlled Point" name and/or number must also be painted above the phone at the "Controlled Point" location.
The "Controlled Point" locations will be designated, and the controlled point numbers assigned, by the Chief Engineer, and signs will be installed only at locations approved by the Chief Engineer.
The controlled point number will be displayed on the train dispatchers "Track Display Panel," and employees contacting the train dispatcher must use the control point number to identify their location.
(View an image of Drawing C.S. 17-B)
The change was reflected in Union Pacific's System Timetable No. 3, dated March 9, 1980, as follows:
(CP) - A location where signals and/or switches of a CTC System are controlled by train dispatcher or control operator.
Controlled Point Number - A number, assigned to a controlled point, which designates the location of the controlled point (to the nearest milepost). When necessary to contact train dispatcher or control operator, employees must use controlled point number to identify their location. (Numbers will be designated in timetable and by bulletin).
There was no mention of "controlled point" in the previous employee timetable, System Timetable No. 2, dated December 10, 1978.
CP Names
At controlled points that already had station or siding names, the C.P. (later simplified to just CP) was added as a prefix to the name. Examples in Utah would be "CP C802 Kaysville" and "CP C753 Provo." Points on the former SP and D&RGW lines in Utah did not receive formal CP numbers until 2006-2007.
CP designations have also been used to pay tribute to persons, such as two adjacent control points, CP Mack (MP 49.0) and CP Michael (MP 49.5) on both ends of Caltrain's Tamien station on the Union Pacific's Coast Subdivision near San Jose, California. These two points were named for locomotive engineer Edward 'Big Mack' McMillan, and fireman Michael G. Passarella, the crew of Amtrak's "San Joaquin" passenger train who died in a 1989 grade crossing accident at Mariposa Road, south of Stockton, California.
CP Letter Prefixes
Before 1979
A review of Union Pacific employee timetables prior to the 1979 Bulletin establishing control points shows that in at least two cases, UP used letter prefixes on important, but paralleling routes to avoid confusion from similar mile posts.
Examples include the use of a "P" prefix for locations on UP's Utah Division Provo Subdivision, dating back to the change in 1976-1977 when the entire subdivision was redesignated with distances from Los Angeles, and the "P" was added because of duplicate mile posts with those on the paralleling Second Subdivision by way of Tooele and Stockton. South-Central District employee timetable No. 2, dated September 1, 1976, used the original mile post numbers, and South-Central District timetable No. 3, dated June 26, 1977, used the newer "P" prefix on mile posts along the Provo Subdivision.
A second example was the "B" prefix for mile posts on the Boise Cutoff in Idaho, which dated from 1947 (Timetable 171, dated September 1, 1947) when instead of its own table, the points on the cutoff were included in the overall listing for the Idaho Division's Fourth Subdivision. Although the "B" prefix Boise Cutoff mile posts continued after the changes in 1998, the control points on the cutoff had the "N" or "P" prefix of other mile posts on the Nampa or Pocatello subdivisions. No other examples of letter prefixes on mile posts are known prior to 1979.
After 1979
After the merger with Missouri Pacific and Western Pacific in 1983, the merger with MKT in 1988, and the merger with Chicago & North Western in 1995, designating control points and matching mile posts on a system-wide basis became a problem. To avoid confusion of control points, Union Pacific began using letter prefixes to avoid confusion with points along the original Union Pacific routes.
The timetables began showing the control point numbers with the issue of System Timetable No. 7 (the first to include the MKT), dated October 7, 1989, although they did not have a dedicated column, like the associated station numbers (also known as Circ7 numbers). A separate column for CP numbers started with System Timetable No. 8, dated April 7, 1991.
The merger with SP in 1996 brought large numbers of new control points, and numerous duplications. Although the designations were delayed until 2000-2002, points along the former SP Coast Line received "CO" as a prefix to their controlled point (mile post) numbers, and points along the former SP Sunset Route received "SP" as a prefix for their controlled points.
All control points on the Coast Line from Camarillo (CP CO413) to Gilroy (CP CO077) had the "CP COXXX" signs in place by 2002.
When UP installed new crossovers at locations on Beaumont Hill in 2000-2001 they installed signs with the "CP SPXXX" on them. On the former SP Sunset Route in eastern Arizona and New Mexico, when the Southern Pacific double tracked between Tucson and Lordsburg in 1994-1995, they gave numbers to the new control points, but no prefix.
There are locations on the former SP Sunset Route in eastern Arizona and New Mexico where the where the mileposts go to four digits, measuring the original distance from San Francisco. These locations are the only locations on UP with mileposts in the thousands. For these locations, UP had to use just an "S" prefix as supposedly the UP computer will only allow five characters for a CP designation. This was on the 301 miles of the Lordsburg Subdivision between Tucson (CP S1000, Vail Crossovers) and El Paso (CP S1301, East Leg Wye).
Controlled points along the former D&RGW received "RG" as a prefix to their controlled point numbers, with points along the former Moffat route receiving the "DS" prefix.
CP Letter Prefixes List
From Area (Service Unit) Timetables, 1998-2015
(List is incomplete; Not all issues available)
| CP Prefix | Location |
| A | Clinton Subdivision (Iowa Area; 1998, 2011) Boone Subdivision (Iowa Area; 1998, 2011) Little Rock Subdivision (North Little Rock Area; 1998, 2012) White Bluff Subdivision (North Little Rock Area; 1998, 2012) McGehee Subdivision (North Little Rock Area; 1998, 2012) Monroe Subdivision (North Little Rock Area; 1998, 2012) |
| AC | Alameda Corridor Subdivision (Los Angeles Area; [2002], 2010) |
| AL | Los Angeles Subdivision (Los Angeles Area; 2010) Alhambra Subdivision (Los Angeles Area; 2010) |
| B | Blair Subdivision (Council Bluffs Area; 1998, 2011) Columbus Subdivision (Council Bluffs Area; 1998, 2011) Kearney Subdivision (Council Bluffs Area; 1998, 2011) North Platte Terminal (North Platte Area; 1998, 2012) Omaha Subdivision (Council Bluffs Area; 2011) |
| C |
Los Angeles Subdivision (Los Angeles Area; 1998, 2010) |
| CB | Corsicana Subdivision (Dallas-Fort Worth Area; 2012, 2015) Jonesboro Subdivision (North Little Rock Area; 2012) Pine Bluff Subdivision (North Little Rock Area; 2012) |
| CO | Santa Barbara Subdivision (Los Angeles Area; 2010) Coast Subdivision (Roseville Area; 2012) |
| D | Hoxie Subdivision (North Little Rock Area; 1998) (changed to Y by 2012) Chester Subdivision (St. Louis Area; 1998, 2013) DeSoto Subdivision (St. Louis Area; 1998, 2013) Sparta Subdivision (St. Louis Area; 1998) Jefferson City Subdivision (St. Louis Area; 1998) |
| DS (not in 1998 issue) |
Craig Subdivision (Denver Area; 2009, 2015) Moffat Tunnel Subdivision (Denver Area; 2009, 2015) Glenwood Springs Subdivision (Denver Area; 2015) |
| E | Ayer Subdivision (Portland Area; 1998, 2011, 2014) Portland Subdivision (Portland Area; 1998, 2011, 2014) LaGrande Subdivision (Portland Area; 2011, 2014) Kenosha Subdivision (Chicago Area; 2009, 2014) Yakima Subdivision (Portland Area; 2011, 2014) |
| EB | Houston East Belt Subdivision (Houston Area; 2011) |
| F | Elko Subdivision (Roseville Area; 1998, 2012) Winnemucca Subdivision (Roseville Area; 1998, 2012) Canyon Subdivision (Roseville Area; 1998, 2012) Sacramento Subdivision (Roseville Area; 1998, 2012) Oakland Subdivision (Roseville Area; 1998, 2012) Milpitas Subdivision (Roseville Area; 1998) Shafter Subdivision (Salt Lake City Area; 1998, 2008, 2011, 2015) |
| FL | Giddings Subdivision (Houston Area; 2011) Cuero Subdivision (Houston Area; 2011) |
| G | Rawlins Subdivision (North Platte Area; 1998, 2012) Pocatello Subdivision (Portland Area; 1998, 2011, 2014) Evanston Subdivision (Salt Lake City Area; 1998, 2008, 2011, 2015) Ogden Subdivision (Salt Lake City Area; 1998, 2011, 2015) Shafter Subdivision (Salt Lake City Area; 1998) |
| H | Palestine Subdivision (Houston Area; 1998, 2011) Houston West Belt Subdivision (Houston Area; 2011) Angleton Subdivision (Houston Area; 2011) Brownsville Subdivision (Houston Area; 2011) Hearne Subdivision (Dallas-Fort Worth Area; 2012) |
| HL | Ennis Subdivision (Dallas-Fort Worth Area; 2012, 2015) |
| I | Villa Grove Subdivision (St. Louis Area; 1998, 2013) Pana Subdivision (St. Louis Area; 1998, 2013) Mt. Vernon Subdivision (St. Louis Area; 1998, 2013) Salem Subdivision (St. Louis Area; 2013) Marion Subdivision (St. Louis Area; 2013) |
| J | Brownsville Subdivision (Houston Area; 1998, 2011) Laredo Subdivision (San Antonio Area; 1998, 2009) |
| K | Limon Subdivision (Denver Area; 1998, 2015) KCT Subdivision (Kansas City Area; 1998) Sharon Springs Subdivision (Salina Area; 1998, 2013) KC Metro Subdivision (Kansas City Area; 2011) |
| L | Livonia Subdivision (Houston Area; 1998) Monroe Subdivision (North Little Rock Area; 1998, 2012) Beaumont Subdivision (Houston Area; 2011) Alexandria Subdivision (Houston Area; 2011) Livonia Subdivision (Houston Area; 2011) Lake Charles Subdivision (Houston Area; 2011) Anchorage Subdivision (Houston Area; 2011) |
| LF | Lafayette Subdivision (Houston Area; 2011) Terminal Subdivision (Houston Area; 2011) |
| LN | Los Nietos Subdivision (Los Angeles Area; 2010) |
| M | River Subdivision (Kansas City Area; 1998, 2011) Sedalia Subdivision (Kansas City Area; 1998, 2011) Martinez Subdivision (Roseville Area; 1998) Jefferson City Subdivision (St. Louis Area; 1998, 2013) KC Metro Subdivision (Kansas City Area; 2011) Fairmont Subdivision (Twin Cities Area; 2011) |
| N | Huntington Subdivision (Portland Area; 1998, 2011, 2014) LaGrande Subdivision (Portland Area; 1998, 2011, 2014) Harvard Subdivision (Chicago Area; 2009, 2014) Kenosha Subdivision (Chicago Area; 2009) Milwaukee Subdivision (Chicago Area; 2009, 2014) Nampa Subdivision (Portland Area; 2011, 2014) |
| NI | Niles Subdivision (Roseville Area; 2012) |
| OK | Duncan Subdivision (Dallas-Fort Worth Area; 2015) |
| P | Nampa Subdivision (Portland Area; 1998, 2011, 2014) Peoria Subdivision (Chicago Area; 2009, 2014) Montana Subdivision (Portland Area; 2011, 2014) Pocatello Subdivision (Portland Area; 2014) |
| PD | San Pedro Subdivision (Los Angeles Area; 2010) |
| PX | Phoenix Subdivision (Sunset Area; 2010, 2014) |
| Q | Fort Worth Subdivision (Dallas-Fort Worth Area; 1998, 2012, 2015) Navasota Subdivision (Houston Area; 1998, 2011) Austin Subdivision (San Antonio Area; 1998, 2009) Waco Subdivision (Dallas-Fort Worth Area; 2012, 2015) Hearne Subdivision (Dallas-Fort Worth Area; 2015) |
| R | Dallas Subdivision (Dallas-Fort Worth Area; 1998) Mineola Subdivision (Dallas-Fort Worth Area; 2012, 2015) Little Rock Subdivision (North Little Rock Area; 2012) |
| RG (not in 1998 issue) |
Tennessee Pass Subdivision (Denver Area; 2009, 2015) |
| RV (not in 1998 issue) |
Elko Subdivision (Roseville Area; 2012) Lakeside Subdivision (Salt Lake City Area; 2008, 2011, 2015) Nevada Subdivision (Roseville Area; 2012) Roseville Subdivision (Roseville Area; 2012) Martinez Subdivision (Roseville Area; 2012) Tracy Subdivision (Roseville Area; 2012) |
| S |
Portland Subdivision (Portland Area; 1998, 2011, 2014) |
| SA | Del Rio Subdivision (San Antonio Area; 2009) Sanderson Subdivision (San Antonio Area; 2009) Valentine Subdivision (Sunset Area; 2010, 2014) Harrisburg Subdivision (Houston Area; 2011) Glidden Subdivision (Houston Area; 2011) |
| SP | Gila Subdivision (Sunset Area; 2010, 2014) Mojave Subdivision (Los Angeles Area; 2010) Yuma Subdivision (Los Angeles Area; 2010) Fresno Subdivision (Roseville Area; 2012) |
| ST | Strang Subdivision (Houston Area; 2011) |
| SX | Sioux City Subdivision (Council Bluffs Area; 2011) Mankato Subdivision (Twin Cities Area; 2011) Worthington Subdivision (Twin Cities Area; 2011) Fairmont Subdivision (Twin Cities Area; 2011) |
| T |
Dallas Subdivision (Dallas-Fort Worth Area; 1998, 2012, 2015) |
| TC | Carrizozo Subdivision (Sunset Area; 2010, 2014) Tucumcari Subdivision (Sunset Area; 2010, 2014) Topeka Subdivision (Salina Area; 2013) Herington Subdivision (Salina Area; 2013) Pratt Subdivision (Salina Area; 2013) |
| TR | Tracy Subdivision (Roseville Area; 2012) |
| U | Mason City Subdivision (Iowa Area; 1998, 2011) Trenton Subdivision (Kansas City Area; 1998, 2011) Cherokee Subdivision (Kansas City Area; 1998, 2011) Albert Lea Subdivision (Twin Cities Area; 1998, 2011) Choctaw Subdivision (Dallas-Fort Worth Area; 2012, 2015) |
| V | Parsons Subdivision (Kansas City Area; 1998, 2011) Coffeyville Subdivision (Kansas City Area; 1998, 2011) Wagoner Subdivision (Kansas City Area; 1998, 2011) |
| VP | Brooklyn Subdivision (Portland Area; 2011, 2014) Cascade Subdivision (Portland Area; 2011, 2014) Black Butte Subdivision (Roseville Area; 2012) Valley Subdivision (Roseville Area; 2012) |
| W | Greeley Subdivision (Denver Area; 1998, 2015) North Platte Terminal (North Platte Area; 1998, 2012) South Morrill Subdivision (North Platte Area; 1998, 2012) Powder River Subdivision (North Platte Area; 1998, 2012) Sidney Subdivision (North Platte Area; 1998, 2012) Laramie Subdivision (North Platte Area; 1998, 2012) Rawlins Subdivision (North Platte Area; 1998, 2012) |
| WI | Wilmington Subdivision (Los Angeles Area; 2010) |
| X |
Little Rock Subdivision (North Little Rock Area; 1998, 2012) |
| Y | Clinton Subdivision (Iowa Area; 1998) Memphis Subdivision (North Little Rock Area; 1998, 2012) Wayne Subdivision (North Little Rock Area; 1998) Geneva Subdivision (Chicago Area; 2009) Hoxie Subdivision (North Little Rock Area; 2012) Wynne Subdivision (North Little Rock Area; 2012) Chicago Subdivision (Chicago Area; 2014) Harvard Subdivision (Chicago Area; 2014) Rockwell Subdivision (Chicago Area; 2014) |
| YR | Yoder Subdivision (North Platte Area; 2012) |
| Z |
Kansas Subdivision (Kansas City Area; 1998, 2011) |
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