Railroad Glossary

An Automatic Block Signal system divides track into blocks protected by wayside signals that display aspects based on the occupancy of the block ahead, without dispatcher intervention.

CTC is a signal and train control system that allows a remote dispatcher to remotely operate switches and signals over a defined territory, managing all train movements from a central location.

Dark territory is railroad track that operates without any signal system, where train movements are governed entirely by track warrants and direct crew communication.

A railroad dispatcher is the operations control employee responsible for authorizing and managing all train movements within an assigned territory, issuing track authorities, and coordinating with crews, MOW, and maintenance departments.

A DPU is a locomotive cut into the middle or rear of a long freight train and controlled remotely from the lead unit to distribute tractive and braking effort along the consist.

Dynamic braking is a braking mode in which a locomotive's traction motors are switched to act as generators, converting kinetic energy into electrical resistance and providing controlled retardation without applying the air brake system.

EOT is the operational shorthand for the rear of a freight train consist and for the electronic device — formally called an ETD — that monitors brake-pipe pressure at that location.

An ETD is the FRA-mandated unit on the trailing car that monitors brake-pipe pressure and transmits status to the locomotive cab.

An event recorder is the FRA-mandated onboard data logger that continuously captures locomotive operating parameters — speed, throttle, brake applications, and signal status — for post-incident analysis.

A geometry car is a purpose-built, instrumented rail vehicle that measures track geometry — gauge, cross-level, surface, alignment, and curvature — with precision sensors to identify defects against FRA standards.

A grade crossing is an at-grade intersection where a railroad track crosses a public road or private driveway, regulated by the FRA and protected by active or passive warning devices.

A hi-rail vehicle is a rubber-tired truck or SUV equipped with retractable steel rail wheels that allow it to operate on both road and railroad track.

A Hot Box Detector is a trackside infrared sensor that measures the temperature of journal bearings on passing cars and alerts the crew to overheated conditions that indicate imminent bearing failure.

A locomotive is the self-propelled power unit that generates tractive effort to move a train consist over a railroad.

Maintenance-of-Way refers to the department, workforce, and activities responsible for inspecting, repairing, and maintaining railroad track and infrastructure.

PTC is the FRA-mandated system that automatically enforces speed restrictions and prevents train-to-train collisions, over-speed derailments, and unauthorized incursions into work zones.

A rail yard is a facility where railcars are sorted, classified, stored, and assembled into outbound trains for revenue service.

A railroad bridge is a structure carrying rail track over a gap — waterway, roadway, or terrain — and is subject to FRA inspection and load-rating requirements.

A roadmaster is the field supervisor responsible for the maintenance, inspection, and regulatory compliance of track and infrastructure within an assigned territory.

A Roadway Worker In Charge is the qualified individual responsible for establishing and maintaining on-track protection for a group of workers fouling the track or right-of-way.

A siding is a section of track connected to the main line at both ends by switches, used for train meets, car storage, and industry switching.

A track inspector is an FRA-qualified railroad employee responsible for visually inspecting assigned track territory on a defined cycle to identify defects and ensure compliance with FRA Track Safety Standards.

A train consist is the complete ordered inventory of locomotives and cars that make up a train, used for crew briefing, air brake testing, and operational planning.

A wayside detector is a fixed trackside device that automatically inspects passing trains for mechanical defects — overheated bearings, wheel impact loads, shifted loads, and other conditions — and broadcasts alerts to the train crew.