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Railroad-Highway Grade Crossing Handbook - Revised Second Edition August 2007
Appendix A: Glossary Table of Contents | Previous | Next




Abandonment. The relinquishment of interest (public or private) in right of way or activity thereon with no intention to reclaim or use again for highway or railroad purposes.

Accident rate. 1) The number of accidents, fatalities, or injuries divided by a measure of vehicle activity to provide a means of comparing accident trends through time. 2) The number of accidents per crossing per year.

Advance preemption. The notification of an approaching train that is forwarded to the highway traffic signal controller unit or assembly by the railroad equipment in advance of the activation of railroad warning devices.

Advance preemption time. The period of time that is the difference between the required maximum highway traffic signal preemption time and the activation of the railroad warning devices.

Allotment. An action by administrative authority making funds available for obligations and expenditures for specified purposes and for certain periods.

Anchors. Rail-fastening devices used to resist the longitudinal movement of rail under traffic and to maintain proper expansion allowance at joint gaps for temperature changes.

Apportionment. An administrative assignment of funds based on a prescribed formula by a governmental unit to another governmental unit for specific purposes and for certain periods.

Appropriation. An act of a legislative body that makes funds available for expenditures with specific limitations as to amount, purpose, and period.

At-grade intersection (crossing). An intersection (crossing) where roadways (and railroads) join or cross at the same level.

Ballast. Material placed on a track roadbed to hold the track in alignment and elevation; it consists of hard principles that are stable, easily tamped, permeable, and resistant to plant growth.

Barrier gate. (Barrier gate arm, warning/barrier gate, vehicle arresting system.) An automatic gate used as adjunct to flashing light signals to provide positive protection by blocking approaching traffic at a highway-rail crossing and preventing vehicle penetration according to the requirements of National Cooperative Highway Research Program Report 350.

Benefit-cost ratio. The economic value of the reduction in fatalities, injuries, and property damage divided by the cost of the collision-reducing measure.

Branch line. A secondary line of railroad usually handling light volumes of traffic.

Cab. The space in a locomotive unit or “MU” car containing the operating controls and providing shelter and seats for the engine crew.

Cantilevered signal structure. A structure that is rigidly attached to a vertical pole and used to provide overhead support of signal units.

Catenary system. A system that consists of overhead supporting cables and a conductor (trolley wire) that supplies electricity to power rolling stock through contact with a pantograph or trolley current-collecting device (trolley pole).

Centralized Traffic Control (CTC). A traffic control system whereby train movements are directed through the remote operation of switches and signals from a central control point.

Clear storage distance. The distance available for vehicle storage measured between 1.8 meters (6 feet) from the rail nearest the intersection to the intersection stop line or the normal stopping point on the highway. At skewed highway-rail grade crossings and intersections, the 1.8-meter (6-foot) distance shall be measured perpendicular to the nearest rail either along the centerline or edge line of the highway, as appropriate, to obtain the shorter distance. Where exit gates are used, the distance available for vehicle storage is measured from the point where the rear of the vehicle would be clear of the exit gate arm. In cases where the exit gate arm is parallel to the track(s) and is not perpendicular to the highway, the distance is measured either along the centerline or edge line of the highway, as appropriate, to obtain the shorter distance.

Comparative negligence. A legal doctrine applicable in negligence suits, according to which the negligence of the plaintiff as well as that of the defendant is taken into account. Damages are based upon the outcome of a comparison of the two and are thus proportioned.

Consist. 1) The makeup or composition (number and specific identity) of a train of vehicles. 2) Contents.

Construction. The actual physical accomplishment of building, improving, or changing a highway-rail grade crossing or other finite facility.

Contract. The written agreement between the contracting agency and the contractor setting forth the obligations of the parties thereunder for the performance of the prescribed work. The contract includes the invitation for bids; proposal; contract form and contract bond; specifications; supplemental specifications; special provisions; general and detailed plans; and notice to proceed. The contract also includes any change orders and agreements required to complete the construction of the work in an acceptable manner, including authorized extensions thereof, all of which constitute one instrument.

Contractor. The individual, partnership, firm corporation, or any acceptable combination thereof, or joint venture, contracting with an agency for performance of prescribed work.

Corridor. A strip of land between two termini within which traffic, topography, environment, and other characteristics are evaluated for transportation purposes.

Cross section. A vertical section of the ground and facilities thereon at right angles to the centerline.

Crossing angle. The angle of 90 degrees or less at which a railroad and a highway intersect.

Crosstie. The wooden or concrete support upon which track rails rest, which holds them to gauge and transfers their load through the ballast to the subgrade.

Culvert. Any structure under the roadway with a clear opening of 20 feet or less measured along the center of the roadway.

Design vehicle. The longest vehicle permitted by statute of the road authority (state or other) on that roadway.

Diagnostic team. A group of knowledgeable representatives of the parties of interest in a highway-rail crossing or a group of crossings.

Do-nothing alternative. An alternative that refers to the existing state of the system.

Dynamic envelope. The clearance required for the train and its cargo overhang due to any combination of loading, lateral motion, or suspension failure.

Dynamic exit gate operating mode. A mode of operation where the exit gate operation is based on the presence of vehicles within the minimum track clearance distance.

Easement. A right to use or control the property of another for a designated purpose.

1.    Drainage easement. An easement for directing the flow of water.

2.    Planting easement. An easement for reshaping roadside areas and establishing, maintaining, and controlling plant growth thereon.

3.    Sight line easement. An easement for maintaining or improving the sight distance.

4.    Slope easement. An easement for cuts or fills.

Economic analysis. Determination of the cost-effectiveness of a project by comparing the benefits derived and the costs incurred in a project.

1.    Cost-benefit analysis. A form of economic evaluation in which input is measured in terms of dollar costs and output is measured in terms of economic benefit of a project as compared to the incurred cost of the project.

2.    Cost-effectiveness analysis. A comparison study between the cost of an improvement (initial plus maintenance) and the benefits it provides. The latter may be derived from collisions reduced, travel time reduced, or increased volume of usage and translated into equivalent dollars saved.

Encroachment. Unauthorized use of highway or railroad right of way or easements as for signs, fences, buildings, etc.

Equipment rental rate. Equipment usage charges usually established on a time or mileage use basis, including direct costs, indirect costs, and depreciation.

Exit gate clearance time. For four-quadrant gate systems, the exit gate clearance time is the amount of time provided to delay the descent of the exit gate arm(s) after entrance gate arm(s) begin to descend.

Exit gate operating mode. For four-quadrant gate systems, the mode of control used to govern the operation of the exit gate arms.

Expenditures. A term applicable to accrual accounting, meaning total charges incurred, including expenses, provision for retirement of debt, and capital outlays. The making of a payment is a disbursement.

Flashing light signals. A warning device consisting of two red signal indications arranged horizontally that are activated to flash alternately when a train is approaching or present at a highway-rail grade crossing.

Force account work. Prescribed work paid for on the basis of actual costs and appropriate additives.

Functional classification. Division of a transportation network into classes or systems, according to the nature of the service they are to provide.

Grade. The rate of ascent or descent of a roadway, expressed as a percent; the change in roadway elevation per unit of horizontal length.

Grade separation. A crossing of two highways, or a highway and a railroad, at different levels.

Guardrails. Traffic barriers used to shield hazardous areas from errant vehicles.

Highway, street, or road. A general term denoting a public way for purposes of vehicular travel, including the entire area within the right of way.

Highway-rail grade crossing. The general area where a highway and a railroad cross at the same level, within which are included the railroad, roadway, and roadside facilities for traffic traversing that area.

Pedestrian crossing. A highway-rail grade crossing used by pedestrians but not by vehicles.

Private crossing. A highway-rail grade crossing that is not a public highway-rail grade crossing, such as grade crossings that are on privately-owned roadways utilized only by the owner’s licensees and invitees.

Public crossing. A highway-rail grade crossing that is on a roadway or a pathway under the jurisdiction of and maintained by a public authority and open to the traveling public.

Interconnection. The electrical connection between the railroad active warning system and the highway traffic signal controller assembly for the purpose of preemption.

Lading. Freight or cargo making up a shipment.

Lane. A strip of roadway used for a single line of vehicles.

1.    Auxiliary lane. The portion of the roadway adjoining the through traveled way for parking, speed change, turning, storage for turning, weaving, truck climbing, or other purposes supplementary to through traffic movement.

2.    Pullout lane. An auxiliary lane provided for removal from the through traffic lane those vehicles required to stop at all highway-rail grade crossings.

3.    Speed-change lane. An auxiliary lane, including tapered areas, primarily for the acceleration or deceleration of vehicles entering or leaving the through traveled way.

4.    Traffic lane. The portion of the traveled way for the movement of a single line of vehicles.

Line haul. The movement of freight over the tracks of a railroad from one town or city to another town or city.

Local freight train. A train with an assigned crew that works between predesignated points. These trains handle the switching outside the jurisdiction of a yard switcher.

Locomotive. A self-propelled unit of on-track equipment designed for moving other rail freight and passenger equipment on rail tracks.

Main line. The principal line or lines of a railway.

Main track. A track extending through yards and between stations, upon which trains are operated by timetable or train order or both, or the use of which is governed by block signals or by centralized traffic control.

Materials. Any substances specified for use in the construction of a project and its appurtenances.

Maximum highway traffic signal preemption time. The maximum amount of time needed following initiation of the preemption sequence for the highway traffic signals to complete the timing of the right-of-way transfer time, queue clearance time, and separation time.

Measure of effectiveness (MOE). A measurable unit or set of units assigned to each evaluation objective. The data collected in the units of the MOE will allow for a determination of the degree of achievement for that objective.

Minimum track clearance distance. For standard two-quadrant railroad warning devices, the minimum track clearance distance is the length along a highway at one or more railroad tracks, measured either from the highway stop line, warning device, or 3.7 meters (12 feet) perpendicular to the track centerline, to 1.8 meters (6 feet) beyond the track(s) measured perpendicular to the far rail, along the centerline or edge line of the highway, as appropriate, to obtain the longer distance.

For four-quadrant gate systems, the minimum track clearance distance is the length along a highway at one or more railroad tracks, measured either from the highway stop line or entrance warning device, to the point where the rear of the vehicle would be clear of the exit gate arm. In cases where the exit gate arm is parallel to the track(s) and is not perpendicular to the highway, the distance is measured either along the centerline or edge of the highway, as appropriate, to obtain the longer distance.

Minimum warning time—through train movements.

The least amount of time active warning devices shall operate prior to the arrival of a train at a highway-rail grade crossing.

Pavement markings. Markings set into the surface of, applied upon, or attached to the pavement for the purpose of regulating, warning, or guiding traffic.

Pavement structure. The combination of subbase, base course, and surface course placed on a subgrade to support the traffic load and distribute it to the roadbed.

1.    Base course. The layer or layers of specified or selected material of designed thickness placed on a subbase or subgrade to support a surface course.

2.    Surface course. One or more layers of a pavement structure designed to accommodate the traffic load, the top layer of which resists skidding, traffic abrasion, and the disintegrating effects of climate. The top layer is sometimes called “wearing course.”

3.    Subbase. The layer or layers of specified or selected material of designed thickness placed on a subgrade to support a base course.

4.    Subgrade. The top surface of a roadbed upon which the pavement structure and shoulders, including curbs, are constructed.

Plaintiff. The person who begins an action at law; the complaining party in an action.

Plans. Contract drawings that show the location, character, and dimensions of the prescribed work, including layouts, profiles, cross sections, and other details.

Precedent. An adjudged case or judicial decision that furnishes a rule or model for deciding a subsequent case that presents the same or similar legal problems.

Preemption. The transfer of normal operation of highway traffic signals to a special control mode.

Preliminary engineering. The work necessary to produce construction plans, specifications, and estimates to the degree of completeness required for undertaking construction thereunder, including locating, surveying, designing, and related work.

Pre-signal. Supplemental highway traffic signal faces operated as part of highway intersection traffic signals, located in a position that controls traffic approaching the highway-rail grade crossing in advance of the intersection.

Queue clearance time. The time required for the design vehicle of maximum length stopped just inside the minimum track clearance distance to start up, move through, and clear the entire minimum track clearance distance. If pre-signals are present, this time shall be long enough to allow the vehicle to move through the intersection or to clear the tracks if there is sufficient clear storage distance. If a four-quadrant gate system is present, this time shall be long enough to permit the exit gate arm to lower after the design vehicle is clear of the minimum track clearance distance.

Rail joint. A fastening designed to unite abutting ends of rail.

Railroad line miles. The aggregate length of road of line-haul railroads. It excludes yard tracks, sidings, and parallel lines. Jointly used track is counted only once.

Railroad track miles. Total miles of railroad track including multiple main tracks, yard tracks, and sidings, owned by both line-haul and switching and terminal companies.

Right of way. A general term denoting land, property, or interest therein, usually in a strip, acquired for or devoted to transportation purposes.

Right-of-way transfer time. The maximum amount of time needed for the worst-case condition, prior to display of the track clearance green interval. This includes any railroad or highway traffic signal control equipment time to react to a preemption call and any traffic control signal green, pedestrian walk and clearance, yellow change, and red clearance intervals for conflicting traffic.

Roadway. The portion of a highway, including shoulders, for vehicular use. A divided highway has two or more roadways.

Salvage value. Estimated residual worth of program or project components at the end of their expected service lives.

Separation time. The component of maximum highway traffic signal preemption time during which the minimum track clearance distance is clear of vehicular traffic prior to the arrival of the train.

Service life. The period of time, in years, in which the components of a program or project can be expected to actively affect collision experience.

Shoulder. The portion of the roadway contiguous with the traveled way primarily for accommodation of stopped vehicles for emergency use and for lateral support of base and surface courses.

Sidewalk. That portion of the roadway primarily constructed for the use of pedestrians.

Simultaneous preemption. Notification of an approaching train is forwarded to the highway traffic signal controller unit or assembly and railroad active warning devices at the same time.

Sovereign immunity. The immunity of a government from being sued in its own courts except with its consent, or other exception.

Statute of limitations. A statute that imposes time limits upon the right to sue in certain cases.

Stopping sight distance. The length of highway required to safely stop a vehicle traveling at a given speed.

Superelevation rate. The rate of rise in cross section of the finished surface of a roadway on a curve, measured from the lowest or inside edge to the highest or outside edge.

Tie plate. A flanged plate between a rail and a crosstie that distributes the rail load over a larger area and helps hold track gauge.

Timed exit gate operating mode. A mode of operation where the exit gate descent is based on a predetermined time interval.

Timetable. 1) The authority for the movement of regular trains subject to the rules; it contains classified schedules with special instructions relating to the movement of trains and engines. 2) A listing of the times at which vehicles are due at specified time points (colloquial).

Tort. Any private or civil wrong by act or omission but not including breach of contract. Some torts may also be crimes.

Track. 1) An assembly of rails, ties, and fastenings over which cars, locomotives, and trains are moved. 2) The width of a wheeled vehicle from wheel to wheel and usually from the outside of the rims.

1.    Double or multiple. Two or more main tracks over which trains may travel in both directions.

2.    Single. 1) The main track on a roadbed having one main track upon which trains are operated in both directions. 2) In multiple-track territory, the process of running all trains, regardless of direction on one track while the other track(s) is (are) temporarily out of service.

Track gauge. The distance between the inside face of the heads of the two rails of a track, measured perpendicular to the center line. (Standard gauge in the United States is 4 to 8.5 inches.)

Traffic control device. A sign, signal, marking, or other device placed on or adjacent to a street or highway by authority of a public body or official having jurisdiction to regulate, warn, or guide traffic.

1.    Active traffic control device. Traffic control devices activated by the approach or presence of a train, such as flashing light signals, automatic gates, and similar devices, as well as manually-operated devices and crossing watchmen, all of which display to motorists positive warning of the approach or presence of a train.

2.    Passive traffic control device. Types of traffic control devices, including signs, markings, and other devices, located at or in advance of grade crossings to indicate the presence of a crossing but that do not change aspect upon the approach or presence of a train.

3.    Traffic control signal. Any device, whether manually, electrically, or mechanically operated, by which traffic is alternately directed to stop or permitted to proceed.

4.    Traffic markings. All lines, patterns, words, colors, or other devices, except signs, set into the surface of, applied upon, or attached to the pavement or curbing or to the objects within or adjacent to the roadway, officially placed for the purpose of regulating, warning, or guiding traffic.

Track miles. The total centerline length of mainline trackage in a corridor; for example, a two-track mainline typically has twice the track miles as route miles.

Traffic operation plan. A program of action designed to improve the utilization of a highway, a street, or highway and street network, through the application of the principles of traffic engineering.

Traffic sign. A device mounted on a fixed or portable support whereby a specific message is conveyed by means of words or symbols, officially erected for the purpose of regulating, warning, or guiding traffic.

Traffic signal. A power-operated traffic control device by which traffic is regulated, warned, or alternately directed to take specific actions.

1.    Cycle time. The time required for one complete sequence of signal indications.

2.    Detectors. Mechanical or electronic devices that sense and signal the presence or passage of vehicular or railroad traffic at one or more points in the roadway or track.

3.    Phase. Those right-of-way and clearance intervals in a cycle assigned to any independent movement(s) of vehicular traffic.

Train. 1) One or more locomotive units with or without connected cars. 2) Two or more vehicles physically connected and operated as a unit.

1.    Through. A freight train operating between major classification yards and serving nonlocal traffic.

2.    Unit. A freight train moving great tonnage of single bulk products between two points coupled with a system of efficient, rapid loading and unloading facilities.

Train orders. Authorization to move a train as given by a train dispatcher either in writing or verbally.

Traveled way. The portion of the roadway for the movement of vehicles, exclusive of shoulders.

Vehicle. A means of carrying or transporting something.

1.    Bicycle. A vehicle having two tandem wheels, propelled solely by human power, upon which any person or persons may ride.

2.    Bus. A self-propelled rubber-tired vehicle designed to accommodate 15 or more passengers and to operate on streets and roads. Federal Motor Carrier Safety Administration regulations define a “bus” for the purposes of highway-rail grade crossing safety as “any motor vehicle designed, constructed, and or used for the transportation of passengers, including taxicabs.” (49 CFR 390.5)

3.    Design vehicle. A selected motor vehicle, the weight, dimensions, and operating characteristics of which are used in highway design.

4.    Motorcycle. A two-wheeled motorized vehicle having one or two saddles and, sometimes, a sidecar with a third supporting wheel.

5.    Passenger car. A motor vehicle, except motorcycles, designed for carrying 10 passengers or less and used for the transportation of persons.

6.    Semitrailer. Any motor vehicle, other than a pole trailer, designed to be drawn by another motor vehicle and constructed so that some part of its weight rests upon the self-propelled towing motor vehicle. (49 CFR 390.5)

7.    Special vehicle. A vehicle whose driver is required by law to stop in advance of all highway-rail grade crossings. Typically, special vehicles include commercial vehicles transporting passengers, trucks carrying hazardous materials, and school buses.

8. Truck tractor. A self-propelled commercial motor vehicle designed and/or used primarily for drawing other vehicles. (49 CFR 390.5)

Vehicle intrusion detection devices. A detector or detectors used as a part of a system incorporating processing logic to detect the presence of vehicles within the minimum track clearance distance and to control the operation of the exit gates.

Volume. The number of vehicles passing a given point during a specified period of time.

1.    Average daily traffic (ADT). The average 24hour volume, being the total volume during a stated period divided by the number of days in that period. Unless otherwise stated, the period is a year.

2.    Design volume. A volume determined for use in design, representing traffic expected to use the highway. Unless otherwise stated, it is an hourly volume.

Warrants. The minimum conditions that would justify the establishment of a particular traffic control regulation or device, usually including items such as traffic volumes, geometries, traffic characteristics, collision experience, etc.

Wayside equipment. The signals, switches, and/or control devices for railroad operations housed within one or more enclosures located along the railroad right of way and/or on railroad property.

Yard. A system of tracks within defined limits provided for making up trains, storing cars, and other purposes.

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