Railroad Terms



Association of American Railroads

American A&S

Alton and Southern (St. Louis Shortline Railroad)

Air Problems

Any issues associated with the train line or air brake system, including leaking gasket, frozen or blocked train line, stuck triple valve.

Angle Bars

Short pieces of steel used to join track sections to other sections or track structures. An angle bar is placed on each side of the sections being joined. Two holes are drilled into each end of the angle bar and also through both track sections. Four bolts with locking washers are fastened through the holes to join the sections. Angle bars also are used to make temporary repairs to a broken section of rail until it can be replaced.

Bad Order

Rail car that has a mechanical defect.

Behind "X" Trims

Trims are sorted tracks of cars in a hump yard pulled out of the sorting tracks and coupled to make up outbound trains. A yard "behind on trims" is behind on its outbound train building.


Beltline Railroad of Chicago (Chicago Shortline Railroad)

Broncos in the Canyon

Motor vehicles, equipped with Hy-Rail attachments enabling them to ride on rails, operated by Engineering employees patrolling track in the Feather River Canyon during rain or snow. They look for slides, washouts and any unsafe track condition. Broncos operate just one mile ahead of trains under special rules and do not use track and time.

Building Trains

Assembling sorted cars in proper sequence for outbound departure.


Train made up of a single "bulk" commodity and car type. Bulk commodities include coal, grain, soda ash and ore.


Car Hire Allowance

A charge issued by the owner of a rail car.

Car Set Out

Bad order in a train that has a mechanical defect and must be "set out" on line for repairs by mechanical road truck.

Crews are Tight

Sufficient crews are available, but rest issues may cause delays to calls.

Crews Short

Not enough crews are available to protect scheduled outbounds and any deadheads/dogcatch events.


Track that joins two main tracks. When a train moves from one main track to another, it "crosses over."

CTC Outage

When track signals (Centralized Traffic Control) are disabled and do not allow signals to be displayed for trains.


A time period scheduled in advance when no trains operate, allowing maintenance employees to work on track or signals.


Movement of a crew from one point to another or to a train by vehicle transportation or by train.


Track intersection where one track can be used at a time.

DPU (Distributed Power Unit)

A locomotive set capable of remote-control operation in conjunction with locomotive units at the train's head end. DPUs are placed in the middle or at the rear of heavy trains (such as coal, grain, soda ash and even manifest), to help climb steep grades, particularly in the West.

Dragging Equipment Detector

Electronic trackside detection system that identifies unusual conditions, such as brake rigging down, lading down or dragging alongside car, and chains or straps on flat cars along the ground.



Elgin, Joliet and Eastern (Chicago Area Shortline Railroad)


Environmental Management Group

En routes

Count of trains destined to a particular yard or terminal that need to be switched. "Strong enroutes" indicates a forecast for a heavy switching workload for that day.

Extra Board

Unassigned engineers or trainmen used to protect vacancies or make up extra crews as needed to protect higher traffic levels.


Heavy metal flangeways that connect track to switches, diamonds, cross-overs and other track structures. Frogs guide wheels from one track structure to another.

Gothenburg AEI Reader

An Automated Equipment Identification reader located east of North Platte that produces train volume counts through one of UP's busiest corridors.

Hot Box

Overheating of the axle hub due to bearing failure. Metal-on-metal friction generates heat and eventually will melt a 6-inch-diameter steel axle.

Hot Shot

Train with very high priority compared to other trains. Other than passenger trains, UP hot shots are intermodal trains that maintain the most expeditious schedules.

Hot Wheels

Overheating of a rail car's wheels due to sticking brakes and brake shoes rubbing against the wheel tread. They can result in thermal cracking if severe.


Count of cars that are sorted in a hump yard.


Trains destined to a "hump" yard. Hump yards are where rail cars are pushed up a hill (hump), uncoupled, and then rolled downhill into remotely controlled sorting tracks. Hump operations are the railroad's most efficient sorting operations, and the North Platte Terminal is UP's biggest hump yard.



Intermodal Container Transfer Facility at Long Beach, Calif.

In the Hole [to go...]

At the meeting point of opposing trains, one train "Holds the Main," the other "Takes the Hole" in a siding.


Los Angeles Transportation Center


Train made up of mixed rail cars (boxcars, tank cars, piggyback cars, etc.).

Mexico Crossings

Number of cars delivered/received on a daily basis between Union Pacific and Mexican railways at border points, such as Laredo, Texas.

O'Fallons Scanner

An Automated Equipment Identification reader located just west of North Platte. These readers count trains arriving and departing North Platte, as well as coal trains moving to and from the PRB.


Omaha Metro Complex (trackage within area defined by the South Omaha-Fremont-Missouri Valley triangle)


Pool Crew Base

Number of crews determined by volumes and agreements to protect traffic levels at specific terminals.

Power Short

Not enough power coming into the terminal to protect the scheduled outbound departures.


Powder River Basin, in northeast Wyoming, a principal source of UP-hauled coal.

Pull Apart

When two sections of rail separate (pull apart) at a point where they are joined. Rail shrinks in extremely cold weather. When the shrinkage pressure gets too severe, rail will pull apart at its weakest point, usually at a joint.


Crew used to bring a train into a terminal when the original crew has insufficient time to complete the trip and a second crew is necessary.

Red Flag Warnings

Weather alerts issued by contract weather service to advise of situations affecting operations and requiring actions.

Relay Power

Changing out a train's locomotives to correct a situation, such as bad order engines/wrong type-class of units for service.


Response Management Communications Center

Ribbon Rail

Welded rail that is delivered in quarter mile length, then further welded after it is laid. Ribbon rail is common in UPRR main lines.


Train that generally is not scheduled to add (pick up) or reduce (set out) rail cars en route.



Temporary track used to avoid an obstacle that blocks movement on the normal track section.

Shooflies often are constructed to allow temporary passage around mudslides during reconstruction.

Shop Count

Number of bad order rail cars (loads/empties) at a repair facility awaiting repair, or number of locomotives at a shop for repairs.

Sidings Blocked

Auxiliary tracks normally used to meet/pass trains now used to hold trains/cuts of cars spacing/staging for terminals.


Short, usually dead-end section of track used to access a facility or loading/unloading ramp. It also can be used to temporarily store equipment.

Tight on Power

Power is adequate to protect departures, but some delays may occur due to late arrival and servicing of locomotives.

Tonnage is Current

No trains holding, switching is current, no delays expected to traffic, resources are adequate to protect operations.

Trackage Rights

The purchase, for a fee, of the right for one railroad to run on tracks owned by another.

Trains Blocked on Line

Trains stopped between primary terminals and switched to further define the car blocks and to facilitate handling at the destination terminal.

Trains Drug Out

Trains moved from origin yard to a siding between terminals to make room in the yard to continue to build trains.

Trains Flagging

When a train crew has authority granted by a dispatcher to "flag" past a signal that is in stop indication due to a defect/event.

Trains Held Out

The number of trains held on line (out) due to lack of room in the destination yard. When a yard's receiving tracks are occupied, the terminal "holds trains out."

Trains Holding

A count of trains being held either for congestion or for a Maintenance of Way curfew. Trains holding also can refer to the HDC Trains Held Report, used to track trains that are not run on schedule due to a critical resource, such as power, crew or track congestion.

Trains Laid Down

Trains with no arrival plan for a terminal. The crews have been removed and power has likely been removed.

Trains Processed

Number of trains operated through a defined area or terminal during a specified time period.

Trains Slotted

Number of trains a terminal can process in a given period of time, usually every 24 hours.

Trains Spacing

Time spacing in which a terminal/subdivision can handle trains, such as one coal train every 30 minutes, one manifest every hour.

Trains Staging

Trains holding at a point on line for release to move into a terminal.

Trains Tied Down

Trains holding on line for relief crews, Maintenance of Way curfew, slot/spacing into a terminal. Power usually is still on the trains.

Trains Walking

When a track defect, such as a broken rail, has been determined by the Engineering Department to be passable at "walking speed."

Trains Yarded

Number of trains a terminal has yarded in a 24-hour period.

Trim Lead

Track used to move cars from the bowl (sorting tracks) to the departure yard, where sorted cars are coupled into an outbound train.


Count of sorted cars built into outbound trains.


UDE - Undesired Emergency

When air pressure contained within the air brake system is released, resulting in the application of train brakes.


When a flood or a flash flood washes away ballast and roadway under track.


Same as curfew, but also can mean holding trains for things other than Maintenance of Way curfews, such as operating passenger trains.