[Code of Federal Regulations]
[Title 49, Volume 4]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR238.5]

[Page 576-583]
 
                        TITLE 49--TRANSPORTATION
 
       CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF 
                             TRANSPORTATION
 
PART 238_PASSENGER EQUIPMENT SAFETY STANDARDS--Table of Contents
 
                            Subpart A_General
 
Sec. 238.5  Definitions.

    As used in this part--
    AAR means the Association of American Railroads.
    APTA means the American Public Transit Association.
    Actuator means a device directly actuated by the movement of the 
brake cylinder piston which provides an indication of the piston travel.
    Administrator means the Administrator of the Federal Railroad 
Administration or the Administrator's delegate.
    Alerter means a device or system installed in the locomotive cab to 
promote continuous, active locomotive engineer attentiveness by 
monitoring select locomotive engineer-induced control activities. If 
fluctuation of a monitored locomotive engineer-induced control activity 
is not detected within a predetermined time, a sequence of audible and 
visual alarms is activated so as to progressively prompt a response by 
the locomotive engineer. Failure by the locomotive engineer to institute 
a change of state in a monitored control, or acknowledge the alerter 
alarm activity through a manual reset provision, results in a penalty 
brake application that brings the locomotive or train to a stop.
    Anti-climbing mechanism means the parts at the ends of adjoining 
vehicles in a train that are designed to engage when subjected to large 
buff loads to prevent the override of one vehicle by another.
    Bind means restrict the intended movement of one or more brake 
system components by obstruction, increased friction, or reduced 
clearance.
    Block of cars means one car or multiple cars in a solid unit coupled 
together for the purpose of being added to, or removed from, a train as 
a solid unit.
    Brake, air or power brake means a combination of devices operated by 
compressed air, arranged in a system, and controlled manually, 
electrically, or pneumatically, by means of which the motion of a rail 
car or locomotive is retarded or arrested.
    Brake, disc means a retardation system used on some rail vehicles, 
primarily passenger equipment, that utilizes flat metal discs as the 
braking surface instead of the wheel tread.
    Brake, dynamic means a train braking system whereby the kinetic 
energy of a moving train is used to generate electric current at the 
locomotive traction motors, which is then dissipated through banks of 
resistor grids or back into the catenary or third rail system.
    Brake, effective means a brake that is capable of producing its 
required designed retarding force on the train. A brake is not effective 
if its piston travel is in excess of the maximum prescribed limits. On 
vehicles equipped with nominal 12-inch stroke brake cylinders, the brake 
is not effective if its piston travel exceeds 10\1/2\ inches.
    Brake indicator means a device, actuated by brake cylinder pressure, 
which indicates whether brakes are applied or released.
    Brake, inoperative means a primary brake that, for any reason, no 
longer applies or releases as intended or is otherwise ineffective.
    Brake, on-tread friction means a braking system that uses a brake 
shoe that acts on the tread of the wheel to retard the vehicle.
    Brake, parking or hand brake means a brake that can be applied and 
released by hand to prevent movement of a stationary rail car or 
locomotive.
    Brake pipe means the system of piping (including branch pipes, angle

[[Page 577]]

cocks, cutout cocks, dirt collectors, hoses, and hose couplings) used 
for connecting locomotives and all rail cars for the passage of air to 
control the locomotive and car brakes.
    Brake, power means ``air brake'' as that term is defined in this 
section.
    Brake, primary means those components of the train brake system 
necessary to stop the train within the signal spacing distance without 
thermal damage to friction braking surfaces.
    Brake, secondary means those components of the train brake system 
which develop supplemental brake retarding force that is not needed to 
stop the train within signal spacing distances or to prevent thermal 
damage to friction braking surfaces.
    Brake shoes or pads aligned with tread or disc means that the 
surface of the brake shoe or pad, respectively, engages the surface of 
the wheel tread or disc, respectively, to prevent localized thermal 
stress.
    Braking system, blended means a braking system where the primary 
brake and one or more secondary brakes are automatically combined to 
stop the train. If the secondary brakes are unavailable, the blended 
brake uses the primary brake alone to stop the train.
    Calendar day means a time period running from one midnight to the 
next midnight on a given date.
    Class I brake test means a complete passenger train brake system 
test and inspection (as further specified in Sec. 238.313) performed by 
a qualified maintenance person to ensure that the air brake system is 
100 percent effective.
    Class IA brake test means a test and inspection (as further 
specified in Sec. 238.315) performed by a qualified person of the air 
brake system on each car in a passenger train to ensure that the brakes 
apply and release on each car in the train in response to train line 
commands.
    Class II brake test means a test and inspection (as further 
specified in Sec. 238.317) performed by a qualified person of brake 
pipe integrity and continuity from the controlling locomotive to the 
rear unit of a passenger train.
    Collision posts means structural members of the end structures of a 
vehicle that extend vertically from the underframe to which they are 
securely attached and that provide protection to occupied compartments 
from an object penetrating the vehicle during a collision.
    Control valves means that part of the air brake equipment on each 
rail car or locomotive that controls the charging, application, and 
release of the air brakes, in response to train line commands.
    Corner posts means structural members located at the intersection of 
the front or rear surface with the side surface of a rail vehicle and 
which extend vertically from the underframe to the roof. Corner posts 
may be combined with collision posts to become part of the end 
structure.
    Crack means a fracture without complete separation into parts, 
except that, in a casting, a shrinkage crack or hot tear that does not 
significantly diminish the strength of the member is not a crack.
    Crash energy management means an approach to the design of rail 
passenger equipment which controls the dissipation of energy during a 
collision to protect the occupied volumes from crushing and to limit the 
decelerations on passengers and crewmembers in those volumes. This may 
be accomplished by designing energy-absorbing structures of low strength 
in the unoccupied volumes of a rail vehicle or passenger train to 
collapse in a controlled manner, while providing higher structural 
strength in the occupied volumes. Energy deflection can also be part of 
a crash energy management approach. Crash energy management can be used 
to help provide anti-climbing resistance and to reduce the risk of train 
buckling during a collision.
    Crash refuge means a volume with structural strength designed to 
maximize the survivability of crewmembers stationed in the locomotive 
cab during a collision.
    Crewmember means a railroad employee called to perform service 
covered by the Federal hours of service laws at 49 U.S.C. 21103 and 
subject to the railroad's operating rules and program of operational 
tests and inspections required in Sec. 217.9 and Sec. 217.11 of this 
chapter.

[[Page 578]]

    Critical buckling stress means the minimum stress necessary to 
initiate buckling of a structural member.
    Emergency brake application means an irretrievable brake application 
resulting in the maximum retarding force available from the train brake 
system.
    Emergency window means that segment of a side-facing glazing panel 
which has been designed to permit rapid and easy removal in an emergency 
situation.
    End structure means the main support structure projecting upward 
from the underframe of a locomotive, passenger car, or other rail 
vehicle. The end structure is securely attached to the underframe at 
each end of a rail vehicle.
    50th-percentile adult male means a person weighing 164 pounds (plus 
or minus 3 pounds) and possessing the following dimensions: erect 
sitting height: 35.7 inches (plus or minus 0.1 inch); hip breadth 
(sitting): 14.7 inches (plus or minus 0.7 inch); hip circumference 
(sitting): 42 inches; waist circumference (sitting): 32 inches (plus or 
minus 0.6 inch); chest depth: 9.3 inches (plus or minus 0.2 inch); and 
chest circumference: 37.4 inches (plus or minus 0.6 inch).
    Foul means restrict the intended movement of one or more brake 
system components because the component is snagged, entangled, or 
twisted.
    FRA means the Federal Railroad Administration.
    Fuel tank, external means a fuel containment volume that extends 
outside the car body structure of a locomotive.
    Fuel tank, internal means a fuel containment volume that does not 
extend outside the car body structure of a locomotive.
    Full-height collision post, corner post, or side frame post means 
any vertical framing member in the rail car body structure that spans 
the distance between the underframe and the roof at the car body section 
where the post is located. For collision posts located at the 
approximate third points laterally of an end frame, the term ``full-
height'' applies to posts that extend and connect to supporting 
structural members in the roof at the location of the posts, or to a 
beam connected to the top of the end-frame and supported by the roof 
rails (or anti-telescoping plate), or to both.
    Full service application means a brake application which results in 
a brake cylinder pressure at the service limiting valve setting or 
equivalent.
    Glazing, end-facing means a glazing panel located where a line 
perpendicular to the exterior surface of the panel makes an angle of 50 
degrees or less with the longitudinal center line of the rail vehicle in 
which the panel is installed. A glazing panel that curves so as to meet 
the definition for both side-facing and end-facing glazing is considered 
end-facing glazing.
    Glazing, exterior means a glazing panel that is an integral part of 
the exterior skin of a rail vehicle and has a surface exposed to the 
outside environment.
    Glazing, side-facing means a glazing panel located where a line 
perpendicular to the exterior surface of the panel makes an angle of 
more than 50 degrees with the longitudinal center line of the rail 
vehicle in which the panel is installed.
    Handrails means safety appliances installed on either side of a rail 
vehicle's exterior doors to assist passengers and crewmembers to safely 
board and depart the vehicle.
    Head end power means power generated on board the locomotive of a 
passenger train used for purposes other than propelling the train, such 
as cooking, heating, illumination, ventilation and air conditioning.
    In passenger service/in revenue service means a train or passenger 
equipment that is carrying, or available to carry, passengers. 
Passengers need not have paid a fare in order for the equipment to be 
considered in passenger or in revenue service.
    In service, when used in connection with passenger equipment, means:
    (1) Passenger equipment subject to this part that is in passenger or 
revenue service in the United States; and
    (2) All other passenger equipment subject to this part in the United 
States, unless the passenger equipment:
    (i) Is being handled in accordance with Sec. Sec. 238.15, 238.17, 
238.305(d), or 238.503(f), as applicable;

[[Page 579]]

    (ii) Is in a repair shop or on a repair track;
    (iii) Is on a storage track and is not carrying passengers; or
    (iv) Has been delivered in interchange but has not been accepted by 
the receiving railroad.
    Interior fitting means any component in the passenger compartment 
which is mounted to the floor, ceiling, sidewalls, or end walls and 
projects into the passenger compartment more than 25 mm (1 in.) from the 
surface or surfaces to which it is mounted. Interior fittings do not 
include side and end walls, floors, door pockets, or ceiling lining 
materials, for example.
    Lateral means the horizontal direction perpendicular to the 
direction of travel.
    Locomotive means a piece of on-track rail equipment, other than hi-
rail, specialized maintenance, or other similar equipment, which may 
consist of one or more units operated from a single control stand with 
one or more propelling motors designed for moving other passenger 
equipment; with one or more propelling motors designed to transport 
freight or passenger traffic, or both; or without propelling motors but 
with one or more control stands. This term does not include a locomotive 
propelled by steam power unless it is used to haul an intercity or 
commuter passenger train. Nor does this term include a freight 
locomotive when used to haul a passenger train due to failure of a 
passenger locomotive.
    Locomotive cab means the compartment or space on board a locomotive 
where the control stand is located and which is normally occupied by the 
engineer when the locomotive is operated.
    Locomotive, cab car means rail rolling equipment intended to provide 
transportation for members of the general public that is without 
propelling motors but equipped with one or more control stands.
    Locomotive, controlling means the locomotive from which the 
locomotive engineer exercises control over the train.
    Locomotive, MU means rail rolling equipment self-propelled by any 
power source and intended to provide transportation for members of the 
general public; however, this term does not include an MU locomotive 
propelled by steam power unless it is used to haul an intercity or 
commuter passenger train.
    Longitudinal means in a direction parallel to the normal direction 
of travel.
    Luminescent material means material that absorbs light energy when 
ambient levels of light are high and emits this stored energy when 
ambient levels of light are low, making the material appear to glow in 
the dark.
    L/V ratio means the ratio of the lateral force that any wheel exerts 
on an individual rail to the vertical force exerted by the same wheel on 
the rail.
    MIL-STD-882 means a military standard issued by the United States 
Department of Defense to provide uniform requirements for developing and 
implementing a system safety plan and program to identify and then 
eliminate the hazards of a system or reduce the associated risk to an 
acceptable level.
    Mph means miles per hour.
    95th-percentile adult male means, except as used in Sec. 
238.447(f)(2), a person weighing 215 pounds and possessing the following 
dimensions: erect sitting height: 38 inches; hip breadth (sitting): 16.5 
inches; hip circumference (sitting): 47.2 inches; waist circumference 
(sitting): 42.5 inches; chest depth: 10.5 inches; and chest 
circumference 44.5 inches.
    Occupied volume means the volume of a rail vehicle or passenger 
train where passengers or crewmembers are normally located during 
service operation, such as the operating cab and passenger seating and 
sleeping areas. The entire width of a vehicle's end compartment that 
contains a control stand is an occupied volume. A vestibule is typically 
not considered occupied, except when it contains a control stand for use 
as a control cab.
    Ordered, as applied to acquisition of equipment, means that the 
acquiring entity has given a notice to proceed to manufacture the 
equipment that represents a firm financial commitment to compensate the 
manufacturer for the contract price of the equipment or for damages if 
the order is nullified. Equipment is not ordered if future exercise of a 
contract option is required

[[Page 580]]

to place the remanufacturing process in motion.
    Override means to climb over the normal coupling or side buffers and 
linking mechanism and impact the end of the adjoining rail vehicle or 
unit above the underframe.
    Passenger car means rail rolling equipment intended to provide 
transportation for members of the general public and includes a self-
propelled car designed to carry passengers, baggage, mail, or express. 
This term includes a passenger coach, cab car, and an MU locomotive. In 
the context of articulated equipment, ``passenger car'' means that 
segment of the rail rolling equipment located between two trucks. This 
term does not include a private car.
    Passenger coach means rail rolling equipment intended to provide 
transportation for members of the general public that is without 
propelling motors and without a control stand.
    Passenger equipment--means
    (1) All powered and unpowered passenger cars, locomotives used to 
haul a passenger car, and any other rail rolling equipment used in a 
train with one or more passenger cars. Passenger equipment includes--
    (i) A passenger coach,
    (ii) A cab car,
    (iii) A MU locomotive,
    (iv) A locomotive not intended to provide transportation for a 
member of the general public that is used to power a passenger train, 
and
    (v) Any non-self-propelled vehicle used in a passenger train, 
including an express car, baggage car, mail car, freight car, or a 
private car.
    (2) In the context of articulated equipment, ``passenger equipment'' 
means a segment of rail rolling equipment located between two trucks 
that is used in a train with one or more passenger cars. This term does 
not include a freight locomotive when used to haul a passenger train due 
to failure of a passenger locomotive.
    Passenger station means a location designated in a railroad's 
timetable where passengers are regularly scheduled to get on or off any 
train.
    Permanent deformation means the undergoing of a permanent change in 
shape of a structural member of a rail vehicle.
    Person means an entity of any type covered under 1 U.S.C. 1, 
including but not limited to the following: a railroad; a manager, 
supervisor, official, or other employee or agent of a railroad; any 
owner, manufacturer, lessor, or lessee of railroad equipment, track, or 
facilities; any independent contractor providing goods or services to a 
railroad; and any employee of such owner, manufacturer, lessor, lessee, 
or independent contractor.
    Piston travel means the amount of linear movement of the air brake 
hollow rod (or equivalent) or piston rod when forced outward by movement 
of the piston in the brake cylinder or actuator and limited by the brake 
shoes being forced against the wheel or disc.
    Power car means a rail vehicle that propels a Tier II passenger 
train or is the lead vehicle in a Tier II passenger train, or both.
    Pre-revenue service acceptance testing plan means a document, as 
further specified in Sec. 238.111, prepared by a railroad that explains 
in detail how pre-revenue service tests of passenger equipment 
demonstrate that the equipment meets Federal safety standards and the 
railroad's own safety requirements.
    Primary responsibility means the task that a person performs during 
at least 50 percent of the time that the person is working. The totality 
of the circumstances will be considered on a case-by-case basis in 
circumstances where an individual does not spend 50 percent of his or 
her workday engaged in any one readily identifiable type of activity. 
Time spent supervising employees engaged in the functions of 
troubleshooting, inspection, testing, maintenance, or repair of train 
brake and mechanical components and systems covered by this part shall 
be considered work which is generally consistent with the function of 
troubleshooting of such systems and components for the purpose of the 
definition of this term and the definition of ``Qualified Maintenance 
Person.''
    Private car means rail rolling equipment that is used only for 
excursion, recreational, or private transportation purposes. A private 
car is not a passenger car.

[[Page 581]]

    Public highway-rail grade crossing means a location where a public 
highway, road or street, including associated sidewalks or pathways, 
crosses one or more active railroad tracks at grade.
    Qualified maintenance person means a qualified person who has 
received, as a part of the training, qualification, and designation 
program required under Sec. 238.109, instruction and training that 
includes ``hands-on'' experience (under appropriate supervision or 
apprenticeship) in one or more of the following functions: 
troubleshooting, inspection, testing, maintenance, or repair of the 
specific train brake and other components and systems for which the 
person is assigned responsibility. This person shall also possess a 
current understanding of what is required to properly repair and 
maintain the safety-critical brake or mechanical components for which 
the person is assigned responsibility. Further, the qualified 
maintenance person shall be a person whose primary responsibility 
includes work generally consistent with the above-referenced functions 
and is designated to:
    (1) Conduct Class I brake tests under this part;
    (2) Conduct exterior calendar day mechanical inspections on MU 
locomotives or other passenger cars and unpowered vehicles under this 
part; or
    (3) Determine whether equipment not in compliance with this part may 
be moved as required by Sec. 238.17.
    Qualified person means a person who has received, as a part of the 
training, qualification, and designation program required under Sec. 
238.109, instruction and training necessary to perform one or more 
functions required under this part. The railroad is responsible for 
determining that the person has the knowledge and skills necessary to 
perform the required function for which the person is assigned 
responsibility. The railroad determines the qualifications and 
competencies for employees designated to perform various functions in 
the manner set forth in this part. Although the rule uses the term 
``qualified person'' to describe a person responsible for performing 
various functions required under this part, a person may be deemed 
qualified to perform some functions but not qualified to perform other 
functions. For example, although a person may be deemed qualified to 
perform the Class II brake test required by this part, that same person 
may or may not be qualified to perform the Class IA brake test or 
authorize the movement of defective equipment under this part. The 
railroad will determine the required functions for which an individual 
will be deemed a ``qualified person'' based upon the instruction and 
training the individual has received pursuant to Sec. 238.109 on a 
particular function.
    Railroad means any form of nonhighway ground transportation that 
runs on rails or electromagnetic guideways and any entity providing such 
transportation, including--
    (i) Commuter or other short-haul railroad passenger service in a 
metropolitan or suburban area and commuter railroad service that was 
operated by the Consolidated Rail Corporation on January 1, 1979; and
    (ii) High speed ground transportation systems that connect 
metropolitan areas, without regard to whether those systems use new 
technologies not associated with traditional railroads; but does not 
include rapid transit operations in an urban area that are not connected 
to the general railroad system of transportation.
    Refresher training means periodic retraining required by a railroad 
for employees or contractors to remain qualified to perform specific 
equipment inspection, testing, or maintenance functions.
    Repair point means a location designated by a railroad where repairs 
of the type necessary occur on a regular basis. A repair point has, or 
should have, the facilities, tools, and personnel qualified to make the 
necessary repairs. A repair point need not be staffed continuously.
    Respond as intended means to produce the result that a device or 
system is designed to produce.
    Rollover strength means the strength provided to protect the 
structural integrity of a rail vehicle in the event the vehicle leaves 
the track and impacts the ground on its side or roof.

[[Page 582]]

    Roof rail means the longitudinal structural member at the 
intersection of the side wall and the roof sheathing.
    Running brake test means a test (as further specified in Sec. 
238.319) performed by a qualified person of a train system or component 
while the train is in motion to verify that the system or component 
functions as intended.
    Running gear defect means any condition not in compliance with this 
part which involves a truck component, a draft system component, a 
wheel, or a wheel component.
    Safety appliance means an appliance required under 49 U.S.C. chapter 
203, excluding power brakes. The term includes automatic couplers, hand 
brakes, sill steps, handholds, handrails, or ladder treads made of steel 
or a material of equal or greater mechanical strength used by the 
traveling public or railroad employees that provide a means for safely 
coupling, uncoupling, or ascending or descending passenger equipment.
    Safety-critical means a component, system, or task that, if not 
available, defective, not functioning, not functioning correctly, not 
performed, or not performed correctly, increases the risk of damage to 
passenger equipment or injury to a passenger, crewmember, or other 
person.
    Semi-permanently coupled means coupled by means of a drawbar or 
other coupling mechanism that requires tools to perform the uncoupling 
operation. Coupling and uncoupling of each semi-permanently coupled unit 
in a train can be performed safely only while at a maintenance or shop 
location where personnel can safely get under a unit or between units.
    Semi-monocoque means a type of rail vehicle construction where the 
shell or skin acts as a single unit with the supporting frame to resist 
and transmit the loads acting on the rail vehicle.
    Shear strength means the ability of a structural member to resist 
forces or components of forces acting perpendicular to compression or 
tension forces, or both, in the member.
    Shock absorbent material means material designed to prevent or 
mitigate injuries due to impact by yielding and absorbing much of the 
energy of impact.
    Side posts means main vertical structural elements in the sides of a 
rail vehicle.
    Side sill means that portion of the underframe or side at the bottom 
of the rail vehicle side wall.
    Single car test means a comprehensive test (as further specified in 
Sec. 238.311) of the functioning of all critical brake system 
components installed on an individual passenger car or unpowered 
vehicle, other than a self-propelled passenger car, used or allowed to 
be used in a passenger train.
    Single car test device means a device capable of controlling the 
application and release of the brakes on an individual passenger car or 
an unpowered vehicle, other than a self-propelled passenger car, through 
pneumatic or electrical means.
    Skin means the outer covering of a fuel tank and a rail vehicle. The 
skin may be covered with another coating of material such as fiberglass.
    Spall, glazing means small pieces of glazing that fly off the back 
surface of the glazing when an object strikes the front surface.
    Switching service means the classification of freight cars according 
to commodity or destination; assembling of cars for train movements; 
changing the position of cars for purposes of loading, unloading, or 
weighing; placing of locomotives and cars for repair or storage; or 
moving of rail equipment in connection with work service that does not 
constitute a train movement.
    Telescope means override an adjoining rail vehicle or unit and 
penetrate into the interior of that adjoining vehicle or unit because of 
compressive forces.
    Terminal means a starting point or ending point of a single 
scheduled trip for a train, where passengers may get on or off a train. 
Normally, this location is a point where the train would reverse 
direction or change destinations.
    Tier I means operating at speeds not exceeding 125 mph.
    Tier II means operating at speeds exceeding 125 mph but not 
exceeding 150 mph.
    Tourist, scenic, historic, or excursion operations means railroad 
operations

[[Page 583]]

that carry passengers, often using antiquated equipment, with the 
conveyance of the passengers to a particular destination not being the 
principal purpose. Train movements of new passenger equipment for 
demonstration purposes are not tourist, scenic, historic, or excursion 
operations.
    Trailer car means a rail vehicle that neither propels a Tier II 
passenger train nor is the leading unit in a Tier II passenger train. A 
trailer car is normally without a control stand and is normally occupied 
by passengers.
    Train means a locomotive unit or locomotive units coupled, with or 
without cars. For the purposes of the provisions of this part related to 
power brakes, the term ``train'' does not include such equipment when 
being used in switching service.
    Train brake communication line means the communication link between 
the locomotive and passenger equipment in a train by which the brake 
commands are transmitted. This may be a pneumatic pipe, electrical line, 
or radio signal.
    Train, commuter means a passenger train providing commuter service 
within an urban, suburban, or metropolitan area. The term includes a 
passenger train provided by an instrumentality of a State or a political 
subdivision of a State.
    Train, long-distance intercity passenger means a passenger train 
that provides service between large cities more than 125 miles apart and 
is not operated exclusively in the National Railroad Passenger 
Corporation's Northeast Corridor.
    Train, passenger means a train that transports or is available to 
transport members of the general public. If a train is composed of a 
mixture of passenger and freight equipment, that train is a passenger 
train for purposes of this part.
    Train, short-distance intercity passenger means a passenger train 
that provides service exclusively on the National Railroad Passenger 
Corporation's Northeast Corridor or between cities that are not more 
than 125 miles apart.
    Train, Tier II passenger means a short-distance or long-distance 
intercity passenger train providing service at speeds that include those 
exceeding 125 mph but not exceeding 150 mph.
    Trainset, passenger means a passenger train.
    Transverse means in a direction perpendicular to the normal 
direction of travel.
    Ultimate strength means the load at which a structural member 
fractures or ceases to resist any load.
    Uncoupling mechanism means the arrangement for operating the coupler 
by any means.
    Underframe means the lower horizontal support structure of a rail 
vehicle.
    Unit means passenger equipment of any type, except a freight 
locomotive when used to haul a passenger train due to failure of a 
passenger locomotive.
    Unoccupied volume means the volume of a rail vehicle or passenger 
train which does not contain seating and is not normally occupied by 
passengers or crewmembers.
    Vehicle, rail means passenger equipment of any type and includes a 
car, trailer car, locomotive, power car, tender, or similar vehicle. 
This term does not include a freight locomotive when used to haul a 
passenger train due to failure of a passenger locomotive.
    Vestibule means an area of a passenger car that normally does not 
contain seating and is used in passing from the seating area to the side 
exit doors.
    Witness plate means a thin foil placed behind a piece of glazing 
undergoing an impact test. Any material spalled or broken from the back 
side of the glazing will dent or mark the witness plate.
    Yard means a system of tracks within defined limits provided for the 
making up of trains, storing of cars, or other purposes.
    Yard air test means a train brake system test conducted using a 
source of compressed air other than a locomotive.
    Yield strength means the ability of a structural member to resist a 
change in length caused by a heavy load. Exceeding the yield strength 
may cause permanent deformation of the member.

[64 FR 25660, May 12, 1999, as amended at 65 FR 41305, July 3, 2000; 67 
FR 19989, Apr. 23, 2002]

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