Parts and Accessories Necessary for Safe Operation

TITLE 49--TRANSPORTATION

CHAPTER III--FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION

PART 393--PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION
 
Sec. 393.1 Scope of the rules of this part.

Source: 53 FR 49384, Dec. 7, 1988, unless otherwise noted.

Every employer and employee shall comply and be conversant with the
requirements and specifications of this part. No employer shall operate
a commercial motor vehicle, or cause or permit it to be operated, unless
it is equipped in accordance with the requirements and specifications of
this part.

Sec. 393.3 Additional equipment and accessories.

Nothing contained in this subchapter shall be construed to prohibit
the use of additional equipment and accessories, not inconsistent with
or prohibited by this subchapter, provided such equipment and
accessories do not decrease the safety of operation of the motor
vehicles on which they are used.

Sec. 393.5 Definitions.

As used in this part, the following words and terms are construed to
mean:

Aggregate working load limit. The summation of the working load
limits or restraining capacity of all devices used to secure an article
of cargo on a vehicle.

Agricultural commodity trailer. A trailer that is designed to
transport bulk agricultural commodities in off-road harvesting sites and
to a processing plant or storage location, as evidenced by skeletal
construction that accommodates harvest containers, a maximum length of
28 feet, and an arrangement of air control lines and reservoirs that
minimizes damage in field operations.

Anchor point. Part of the structure, fitting or attachment on a
vehicle or article of cargo to which a tiedown is attached.

Antilock Brake System or ABS means a portion of a service brake
system that automatically controls the degree of rotational wheel slip
during braking by:

(1) Sensing the rate of angular rotation of the wheels;

(2) Transmitting signals regarding the rate of wheel angular
rotation to one or more controlling devices which interpret those
signals and generate responsive controlling output signals; and

(3) Transmitting those controlling signals to one or more modulators
which adjust brake actuating forces in response to those signals.

Article of cargo. A unit of cargo, other than a liquid, gas, or
aggregate that lacks physical structure (e.g., grain, gravel, etc.)
including articles grouped together so that they can be handled as a
single unit or unitized by wrapping, strapping, banding or edge
protection device(s).

Bell pipe concrete. Pipe whose flanged end is of larger diameter
than its barrel.

Blocking. A structure, device or another substantial article placed
against or around an article of cargo to prevent horizontal movement of
the article of cargo.

Bracing. A structure, device, or another substantial article placed
against an article of cargo to prevent it from tipping, that may also
prevent it from shifting.

Brake. An energy conversion mechanism used to stop, or hold a
vehicle stationary.

Brake tubing/hose. Metallic brake tubing, nonmetallic brake tubing
and brake hose are conduits or lines used in a brake system to transmit
or contain the medium (fluid or vacuum) used to apply the motor
vehicle's brakes.

Bus. A vehicle designed to carry more than 15 passengers, including
the driver.

Chassis. The load-supporting frame in a truck or trailer, exclusive
of any appurtenances which might be added to accommodate cargo.

Clearance lamp. A lamp used on the front and the rear of a motor
vehicle to indicate its overall width and height.

Container chassis. A semitrailer of skeleton construction limited to
a bottom frame, one or more axles, specially built and fitted with
locking devices for the transport of cargo containers, so that when the
chassis and container are assembled, the units serve the same function
as an over the road trailer.

Converter dolly. A motor vehicle consisting of a chassis equipped
with one or more axles, a fifth wheel and/or equivalent mechanism, and
drawbar, the attachment of which converts a semitrailer to a full
trailer.

Curb weight. The weight of a motor vehicle with standard equipment,
maximum capacity of fuel, oil, and coolant; and, if so equipped, air
conditioning and additional weight of optional engine. Curb weight does
not include the driver.

Dunnage. All loose materials used to support and protect cargo.

Dunnage bag. An inflatable bag intended to fill otherwise empty
space between articles of cargo, or between articles of cargo and the
wall of the vehicle.

Edge protector. A device placed on the exposed edge of an article to
distribute tiedown forces over a larger area of cargo than the tiedown
itself, to protect the tie-down and/or cargo from damage, and to allow
the tiedown to slide freely when being tensioned.

Emergency brake system. A mechanism designed to stop a vehicle after
a single failure occurs in the service brake system of a part designed
to contain compressed air or brake fluid or vacuum (except failure of a
common valve, manifold brake fluid housing or brake chamber housing).

Fifth wheel. A device mounted on a truck tractor or similar towing
vehicle (e.g., converter dolly) which interfaces with and couples to the
upper coupler assembly of a semitrailer.

Frame vehicle. A vehicle with skeletal structure fitted with one or
more bunk units for transporting logs. A bunk unit consists of U-shaped
front and rear bunks that together cradle logs. The bunks are welded,
gusseted or otherwise firmly fastened to the vehicle's main beams, and
are an integral part of the vehicle.

Friction mat. A device placed between the deck of a vehicle and
article of cargo, or between articles of cargo, intended to provide greater
friction than exists naturally between these surfaces.

Fuel tank fitting. Any removable device affixed to an opening in the
fuel tank with the exception of the filler cap.

g. The acceleration due to gravity, 32.2 ft/sec\2\ (9.81 m/sec\2\).
Grommet. A device that serves as a support and protection to that
which passes through it.

Hazard warning signal. Lamps that flash simultaneously to the front
and rear, on both the right and left sides of a commercial motor
vehicle, to indicate to an approaching driver the presence of a
vehicular hazard.

Head lamps. Lamps used to provide general illumination ahead of a
motor vehicle.

Heater. Any device or assembly of devices or appliances used to heat
the interior of any motor vehicle. This includes a catalytic heater
which must meet the requirements of Sec. 177.834(1) of this title when
flammable liquid or gas is transported.

Heavy hauler trailer. A trailer with one or more of the following
characteristics:

(1) Its brake lines are designed to adapt to separation or extension
of the vehicle frame; or

(2) Its body consists only of a platform whose primary cargo-
carrying surface is not more than 40 inches above the ground in an
unloaded condition, except that it may include sides that are designed
to be easily removable and a permanent ``front-end structure'' as that
term is used in Section 393.106 of this title.

Hook-lift container. A specialized container, primarily used to
contain and transport materials in the waste, recycling, construction/
demolition and scrap industries, which is used in conjunction with
specialized vehicles, in which the container is loaded and unloaded onto
a tilt frame body by an articulating hook-arm.

Identification lamps. Lamps used to identify certain types of
commercial motor vehicles.

Integral securement system. A system on certain roll-on/roll-off
containers and hook-lift containers and their related transport vehicles
in which compatible front and rear hold down devices are mated to
provide securement of the complete vehicle and its articles of cargo.

Lamp. A device used to produce artificial light.

Length of a manufactured home. The largest exterior length in the
traveling mode, including any projections which contain interior space.
Length does not include bay windows, roof projections, overhangs, or
eaves under which there is no interior space, nor does it include
drawbars, couplings or hitches.

License plate lamp. A lamp used to illuminate the license plate on
the rear of a motor vehicle.

Longwood. All logs that are not shortwood, i.e., are over 4.9 m (16
feet) long. Such logs are usually described as long logs or treelength.

Low chassis vehicle. (1) A trailer or semitrailer manufactured on or
after January 26, 1998, having a chassis which extends behind the
rearmost point of the rearmost tires and which has a lower rear surface
that meets the guard width, height, and rear surface requirements of
Sec. 571.224 in effect on the date of manufacture, or a subsequent
edition.

(2) A motor vehicle, not described by paragraph (1) of this
definition, having a chassis which extends behind the rearmost point of
the rearmost tires and which has a lower rear surface that meets the
guard configuration requirements of Sec. 393.86(b)(1).

Manufactured home means a structure, transportable in one or more
sections, which in the traveling mode, is eight body feet or more in
width or forty body feet or more in length, or, when erected on site, is
three hundred twenty or more square feet, and which is built on a
permanent chassis and designed to be used as a dwelling with or without
a permanent foundation when connected to the required utilities, and
includes the plumbing, heating, air-conditioning, and electrical systems
contained therein. Calculations used to determine the number of square
feet in a structure will be based on the structure's exterior dimensions
measured at the largest horizontal projections when erected on site.
These dimensions will include all expandable rooms, cabinets, and other projections containing interior space, but do not include bay
windows. This term includes all structures which meet the above
requirements except the size requirements and with respect to which the
manufacturer voluntarily files a certification pursuant to 24 CFR
3282.13 and complies with the standards set forth in 24 CFR part 3280.

Parking brake system. A brake system used to hold a vehicle
stationary.

Play. Any free movement of components.

Pulpwood trailer. A trailer or semitrailer that is designed
exclusively for harvesting logs or pulpwood and constructed with a
skeletal frame with no means for attachment of a solid bed, body, or
container.

Rail vehicle. A vehicle whose skeletal structure is fitted with
stakes at the front and rear to contain logs loaded crosswise.
Rear extremity. The rearmost point on a motor vehicle that falls
above a horizontal plane located 560 mm (22 inches) above the ground and
below a horizontal plane located 1,900 mm (75 inches) above the ground
when the motor vehicle is stopped on level ground; unloaded; its fuel
tanks are full; the tires (and air suspension, if so equipped) are
inflated in accordance with the manufacturer's recommendations; and the
motor vehicle's cargo doors, tailgate, or other permanent structures are
positioned as they normally are when the vehicle is in motion.
Nonstructural protrusions such as taillamps, rubber bumpers, hinges and
latches are excluded from the determination of the rearmost point.

Reflective material. A material conforming to Federal Specification
L-S-300, ``Sheeting and Tape, Reflective; Non-exposed Lens, Adhesive
Backing,'' (September 7, 1965) meeting the performance standard in
either Table 1 or Table 1A of SAE Standard J594f, ``Reflex Reflectors''
(January, 1977).

Reflex reflector. A device which is used on a vehicle to give an
indication to an approaching driver by reflected lighted from the lamps
on the approaching vehicle.

Saddle-mount. A device, designed and constructed as to be readily
demountable, used in driveaway-towaway operations to perform the
functions of a conventional fifth wheel:

(1) Upper-half. Upper-half of a ``saddle-mount'' means that part of
the device which is securely attached to the towed vehicle and maintains
a fixed position relative thereto, but does not include the ``king-
pin;''

(2) Lower-half. Lower-half of a ``saddle-mount'' means that part of
the device which is securely attached to the towing vehicle and
maintains a fixed position relative thereto but does not include the
``king-pin;'' and

(3) King-pin. King-pin means that device which is used to connect
the ``upper-half'' to the ``lower-half'' in such manner as to permit
relative movement in a horizontal plane between the towed and towing
vehicles.

Service brake system. A primary brake system used for slowing and
stopping a vehicle.

Shoring bar. A device placed transversely between the walls of a
vehicle and cargo to prevent cargo from tipping or shifting.

Shortwood. All logs typically up to 4.9 m (16 feet) long. Such logs
are often described as cut-up logs, cut-to-length logs, bolts or
pulpwood. Shortwood may be loaded lengthwise or crosswise, though that
loaded crosswise is usually no more than 2.6 m (102 inches) long.

Sided vehicle. A vehicle whose cargo compartment is enclosed on all
four sides by walls of sufficient strength to contain articles of cargo,
where the walls may include latched openings for loading and unloading,
and includes vans, dump bodies, and a sided intermodal container carried
by a vehicle.

Side extremity. The outermost point on a side of the motor vehicle
that is above a horizontal plane located 560 mm (22 inches) above the
ground, below a horizontal plane located 1,900 mm (75 inches) above the
ground, and between a transverse vertical plane tangent to the rear
extremity of the vehicle and a transverse vertical plane located 305 mm
(12 inches) forward of that plane when the vehicle is unloaded; its fuel
tanks are full; and the tires (and air suspension, if so equipped) are
inflated in accordance with the manufacturer's recommendations. Non-
structural protrusions such as taillights, hinges and latches are excluded from the determination of the outermost point.

Side marker lamp (Intermediate). A lamp shown to the side of a
trailer to indicate the approximate middle of a trailer 30 feet or more
in length.

Side marker lamps. Lamps used on each side of a trailer to indicate
its overall length.

Special purpose vehicle. (1) A trailer or semitrailer manufactured
on or after January 26, 1998, having work-performing equipment that,
while the motor vehicle is in transit, resides in or moves through the
area that could be occupied by the horizontal member of the rear impact
guard, as defined by the guard width, height and rear surface
requirements of Sec. 571.224 (paragraphs S5.1.1 through S5.1.3), in
effect on the date of manufacture, or a subsequent edition.

(2) A motor vehicle, not described by paragraph (1) of this
definition, having work-performing equipment that, while the motor
vehicle is in transit, resides in or moves through the area that could
be occupied by the horizontal member of the rear impact guard, as
defined by the guard width, height and rear surface requirements of
Sec. 393.86(b)(1).

Steering wheel lash. The condition in which the steering wheel may
be turned through some part of a revolution without associated movement
of the front wheels.

Stop lamps. Lamps shown to the rear of a motor vehicle to indicate
that the service brake system is engaged.

Tail lamps. Lamps used to designate the rear of a motor vehicle.

Tiedown. A combination of securing devices which forms an assembly
that attaches articles of cargo to, or restrains articles of cargo on, a
vehicle or trailer, and is attached to anchor point(s).

Tractor-pole trailer. A combination vehicle that carries logs
lengthwise so that they form the body of the vehicle. The logs are
supported by a bunk located on the rear of the tractor, and another bunk
on the skeletal trailer. The tractor bunk may rotate about a vertical
axis, and the trailer may have a fixed, scoping, or cabled reach, or
other mechanical freedom, to allow it to turn.

Turn signals. Lamps used to indicate a change in direction by
emitting a flashing light on the side of a motor vehicle towards which a
turn will be made.

Upper coupler assembly. A structure consisting of an upper coupler
plate, king-pin and supporting framework which interfaces with and
couples to a fifth wheel.

Upper coupler plate. A plate structure through which the king-pin
neck and collar extend. The bottom surface of the plate contacts the
fifth wheel when coupled.

Void filler. Material used to fill a space between articles of cargo
and the structure of the vehicle that has sufficient strength to prevent
movement of the articles of cargo.

Well. The depression formed between two cylindrical articles of
cargo when they are laid with their eyes horizontal and parallel against
each other.

Wheels back vehicle. (1) A trailer or semitrailer manufactured on or
after January 26, 1998, whose rearmost axle is permanently fixed and is
located such that the rearmost surface of the tires (of the size
recommended by the vehicle manufacturer for the rear axle) is not more
than 305 mm (12 inches) forward of the transverse vertical plane tangent
to the rear extremity of the vehicle.

(2) A motor vehicle, not described by paragraph (1) of this
definition, whose rearmost axle is permanently fixed and is located such
that the rearmost surface of the tires (of the size recommended by the
vehicle manufacturer for the rear axle) is not more than 610 mm (24
inches) forward of the transverse vertical plane tangent to the rear
extremity of the vehicle.

Width of a manufactured home. The largest exterior width in the
traveling mode, including any projections which contain interior space.
Width does not include bay windows, roof projections, overhangs, or
eaves under which there is no interior space.

Working load limit (WLL). The maximum load that may be applied to a 
component of a cargo securement system during normal service, usually
assigned by the manufacturer of the component.

Sec. 393.7 Matter incorporated by reference.

(a) Incorporation by reference. Part 393 includes references to
certain matter or materials, as listed in paragraph (b) of this section.
The text of the materials is not included in the regulations contained
in part 393. The materials are hereby made a part of the regulations in
part 393. The Director of the Federal Register has approved the
materials incorporated by reference in accordance with 5 U.S.C. 552(a)
and 1 CFR part 51. For materials subject to change, only the specific
version approved by the Director of the Federal Register and specified
in the regulation are incorporated. Material is incorporated as it
exists on the date of the approval and a notice of any change in these
materials will be published in the Federal Register.

(b) Matter or materials referenced in part 393. The matter or
materials listed in this paragraph are incorporated by reference in the
corresponding sections noted.

(1) Highway Emergency Signals, Fourth Edition, Underwriters
Laboratories, Inc., UL No. 912, July 30, 1979, (with an amendment dated
November 9, 1981), incorporation by reference approved for
Sec. 393.95(j).

(2) Standard Specification for Strapping, Flat Steel and Seals,
American Society for Testing and Materials (ASTM), D3953-97, February
1998, incorporation by reference approved for Sec. 393.104(e).

(3) Welded Steel Chain Specifications, National Association of Chain
Manufacturers, November 15, 1999, incorporation by reference approved
for Sec. 393.104(e).

(4) Recommended Standard Specification for Synthetic Web Tiedowns,
Web Sling and Tiedown Association, WSTDA-T1, 1998, incorporation by
reference approved for Sec. 393.104(e).

(5) Wire Rope Users Manual, 2nd Edition, Wire Rope Technical Board
November 1985, incorporation by reference approved for Sec. 393.104(e).

(6) Cordage Institute rope standards approved for incorporation into
Sec. 393.104(e):

(i) PETRS-2, Polyester Fiber Rope, 3-Strand and 8-Strand
Constructions, January 1993;

(ii) PPRS-2, Polypropylene Fiber Rope, 3-Strand and 8-Strand
Constructions, August 1992;

(iii) CRS-1, Polyester/Polypropylene Composite Rope Specifications,
Three-Strand and Eight-Strand Standard Construction, May 1979;

(iv) NRS-1, Nylon Rope Specifications, Three-Strand and Eight-Strand
Standard Construction, May 1979; and

(v) C-1, Double Braided Nylon Rope Specifications DBN, January 1984.

(c) Availability. The materials incorporated by reference are
available as follows:

(1) Standards of the Underwriters Laboratories, Inc. Information and
copies may be obtained by writing to: Underwriters Laboratories, Inc.,
333 Pfingsten Road, Northbrook, Illinois 60062.

(2) Specifications of the American Society for Testing and
Materials. Information and copies may be obtained by writing to:
American Society for Testing and Materials, 100 Barr Harbor Drive, West
Conshohocken, Pennsylvania 19428-2959.

(3) Specifications of the National Association of Chain
Manufacturers. Information and copies may be obtained by writing to:
National Association of Chain Manufacturers, P.O. Box 22681, Lehigh
Valley, Pennsylvania 18002-2681.

(4) Specifications of the Web Sling and Tiedown Association.
Information and copies may be obtained by writing to: Web Sling and
Tiedown Association, Inc., 5024-R Campbell Boulevard, Baltimore,
Maryland 21236-5974.

(5) Manuals of the Wire Rope Technical Board. Information and copies
may be obtained by writing to: Wire Rope Technical Committee, P.O. Box
849, Stevensville, Maryland 21666.

(6) Standards of the Cordage Institute. Information and copies may
be obtained by writing to: Cordage Institute, 350 Lincoln Street,
115, Hingham, Massachusetts 02043.

(7)-(9) [Reserved].

(10) All of the materials incorporated by reference are available
for inspection at:

(i) The Federal Motor Carrier Safety Administration, Office of Bus
and Truck Standards and Operations, 400 Seventh Street, SW., Washington,
DC 20590; and

(ii) The Office of the Federal Register, 800 North Capitol Street,
NW, Suite 700, Washington, DC.

Sec. 393.9 Lamps operable.

All lamps required by this subpart shall be capable of being
operated at all times.

Sec. 393.11 Lighting devices and reflectors.

The following Table 1 sets forth the required color, position, and
required lighting devices by type of commercial motor vehicle. Diagrams
illustrating the locations of lighting devices and reflectors, by type
and size of commercial motor vehicle, are shown immediately following
Table 1. All lighting devices on motor vehicles placed in operation
after March 7, 1989, must meet the requirements of 49 CFR 571.108 in
effect at the time of manufacture of the vehicle. Motor vehicles placed
in operation on or before March 7, 1989, must meet either the
requirements of this subchapter or part 571 of this title in effect at
the time of manufacture.

Sec. 393.13 Retroreflective sheeting and reflex reflectors, requirements for semitrailers and trailers manufactured before December 1, 1993.

(a) Applicability. All trailers and semitrailers manufactured prior
to December 1, 1993, which have an overall width of 2,032 mm (80 inches)
or more and a gross vehicle weight rating of 4,536 kg (10,001 pounds) or
more, except trailers that are manufactured exclusively for use as
offices or dwellings, pole trailers (as defined in Sec. 390.5 of this
subchapter), and trailers transported in a driveaway-towaway operation,
must be equipped with retroreflective sheeting or an array of reflex
reflectors that meet the requirements of this section. Motor carriers
operating trailers, other than container chassis (as defined in Sec. 393.5), 
have until June 1, 2001, to comply with the requirements of
this section. Motor carriers operating container chassis have until
December 1, 2001, to comply with the requirements of this section.

(b) Retroreflective sheeting and reflex reflectors. Motor carriers
are encouraged to retrofit their trailers with a conspicuity system that
meets all of the requirements applicable to trailers manufactured on or
after December 1, 1993, including the use of retroreflective sheeting or
reflex reflectors in a red and white pattern (see Federal Motor Vehicle
Safety Standard No. 108 (49 CFR 571.108), S5.7, Conspicuity systems).
Motor carriers which do not retrofit their trailers to meet the
requirements of FMVSS No. 108, for example by using an alternative color
pattern, must comply with the remainder of this paragraph and with
paragraph (c) or (d) of this section. Retroreflective sheeting or reflex
reflectors in colors or color combinations other than red and white may
be used on the sides or lower rear area of the semitrailer or trailer
until June 1, 2009. The alternate color or color combination must be
uniform along the sides and lower rear area of the trailer. The
retroreflective sheeting or reflex reflectors on the upper rear area of
the trailer must be white and conform to the requirements of FMVSS No.
108 (S5.7). Red retroreflective sheeting or reflex reflectors shall not
be used along the sides of the trailer unless it is used as part of a
red and white pattern. Retroreflective sheeting shall have a width of at
least 50 mm (2 inches).

(c) Locations for retroreflective sheeting--

(1) Sides. Retroreflective sheeting shall be applied to each side of the trailer or
semitrailer. Each strip of retroreflective sheeting shall be positioned
as horizontally as practicable, beginning and ending as close to the
front and rear as practicable. The strip need not be continuous but the
sum of the length of all of the segments shall be at least half of the
length of the trailer and the spaces between the segments of the strip
shall be distributed as evenly as practicable. The centerline for each
strip of retroreflective sheeting shall be between 375 mm (15 inches)
and 1,525 mm (60 inches) above the road surface when measured with the
trailer empty or unladen, or as close as practicable to this area. If
necessary to clear rivet heads or other similar obstructions, 50 mm (2
inches) wide retroreflective sheeting may be separated into two 25 mm (1
inch) wide strips of the same length and color, separated by a space of
not more than 25 mm (1 inch).

(2) Lower rear area. The rear of each trailer and semitrailer must
be equipped with retroreflective sheeting. Each strip of retroreflective
sheeting shall be positioned as horizontally as practicable, extending
across the full width of the trailer, beginning and ending as close to
the extreme edges as practicable. The centerline for each of the strips
of retroreflective sheeting shall be between 375 mm (15 inches) and
1,525 mm (60 inches) above the road surface when measured with the
trailer empty or unladen, or as close as practicable to this area.

(3) Upper rear area. Two pairs of white strips of retroreflective
sheeting, each pair consisting of strips 300 mm (12 inches) long, must
be positioned horizontally and vertically on the right and left upper
corners of the rear of the body of each trailer and semitrailer, as
close as practicable to the top of the trailer and as far apart as
practicable. If the perimeter of the body, as viewed from the rear, is
not square or rectangular, the strips may be applied along the
perimeter, as close as practicable to the uppermost and outermost areas
of the rear of the body on the left and right sides.

(d) Locations for reflex reflectors.--

(1) Sides. Reflex reflectors shall be applied to each side of the 
trailer or semitrailer. Each array of reflex reflectors shall be positioned 
as horizontally as practicable,beginning and ending as close to the front 
and rear as practicable. The array need not be continuous but the sum 
of the length of all of the array segments shall be at least half of the 
length of the trailer and the spaces between the segments of the strip 
shall be distributed as evenly as practicable. The centerline for each array 
of reflexreflectors shall be between 375 mm (15 inches) and 1,525 mm 
(60 inches)above the road surface when measured with the trailer empty 
or unladen, or as close as practicable to this area. The center of each 
reflector shall not be more than 100 mm (4 inches) from the center 
of each adjacent reflector in the segment of the array. If reflex reflectors 
are arranged in an alternating color pattern, the length of reflectors of the 
first color shall be as closeas practicable to the length of the reflectors of 
the second color.

(2) Lower rear area. The rear of each trailer and semitrailer must
be equipped with reflex reflectors. Each array of reflex reflectors
shall be positioned as horizontally as practicable, extending across the
full width of the trailer, beginning and ending as close to the extreme
edges as practicable. The centerline for each array of reflex reflectors
shall be between 375 mm (15 inches) and 1,525 mm (60 inches) above the
road surface when measured with the trailer empty or unladen, or as
close as practicable to this area. The center of each reflector shall
not be more than 100 mm (4 inches) from the center of each adjacent
reflector in the segment of the array.

(3) Upper rear area. Two pairs of white reflex reflector arrays,
each pair at least 300 mm (12 inches) long, must be positioned
horizontally and vertically on the right and left upper corners of the
rear of the body of each trailer and semitrailer, as close as
practicable to the top of the trailer and as far apart as practicable.
If the perimeter of the body, as viewed from the rear, is not square or
rectangular, the arrays may be applied along the perimeter, as close as
practicable to the uppermost and outermost areas of the rear of the body
on the left and right sides. The center of each reflector shall not be
more than 100 mm (4 inches) from the center of each adjacent reflector
in the segment of the array.

Sec. 393.17 Lamps and reflectors--combinations in driveaway-towaway operation.

A combination of motor vehicles engaged in driveaway-towaway
operation must be equipped with operative lamps and reflectors
conforming to the rules in this section.

(a) The towing vehicle must be equipped as follows:

(1) On the front, there must be at least two headlamps, an equal
number at each side, two turn signals, one at each side, and two
clearance lamps, one at each side.

(2) On each side, there must be at least one side-marker lamp,
located near the front of the vehicle.

(3) On the rear, there must be at least two tail lamps, one at each
side, and two stop lamps, one at each side.

(b) Except as provided in paragraph (c) of this section, the
rearmost towed vehicle of the combination (including the towed vehicle
or a tow-bar combination, the towed vehicle of a single saddle-mount
combination, and the rearmost towed vehicle of a double or triple
saddle-mount combination) or, in the case of a vehicle full-mounted on a
saddle-mount vehicle, either the full-mounted vehicle or the rearmost
saddle-mounted vehicle must be equipped as follows:

(1) On each side, there must be at least one side-marker lamp,
located near the rear of the vehicle.

(2) On the rear, there must be at least two tail lamps, two stop
lamps, two turn signals, two clearance lamps, and two reflectors, one of
each type at each side. In addition, if any vehicle in the combination
is 80 inches or more in overall width, there must be three
identification lamps on the rear.

(c) If the towed vehicle in a combination is a mobile structure
trailer, it must be equipped in accordance with the following lighting
devices. For the purposes of this part, mobile structure trailer means a
trailer that has a roof and walls, is at least 10 feet wide, and can be
used off road for dwelling or commercial purposes.

(1) When the vehicle is operated in accordance with the terms of a
special permit prohibiting operation during the times when lighted lamps
are required under Sec. 392.30, it must have on the rear--

(i) Two stop lamps, one on each side of the vertical centerline, at
the same height, and as far apart as practicable;

(ii) Two tail lamps, one on each side of the vertical centerline, at
the same height, and as far apart as practicable;

(iii) Two red reflex reflectors, one on each side of the vertical
centerline, at the same height, and as far apart as practicable; and

(iv) Two turn signal lamps, one on each side of the vertical
centerline, at the same height, and as far apart as practicable.

(2) At all other times, the vehicle must be equipped as specified in
paragraph (b) of this section.

(d) An intermediate towed vehicle in a combination consisting of
more than two vehicles (including the first saddle-mounted vehicle of a
double saddle-mount combination and the first and second saddle-mount
vehicles of a triple saddle-mount combination) must have one side-marker
lamp on each side, located near the rear of the vehicle.

Sec. 393.19 Requirements for turn signaling systems.

(a) Every bus, truck, or truck tractor shall be equipped with a
signaling system that in addition to signaling turning movements shall
have a switch or combination of switches that will cause the two front
turn signals and the two rear turn signals to flash simultaneously as a
vehicular traffic hazard warning as required by Sec. 392.22 with the
ignition on or off.

(b) Every semitrailer and full trailer shall be equipped so as to
have the two rear turn signals to flash simultaneously with the two
front turn signals of the towing vehicle as a vehicular traffic hazard
warning as required by Sec. 392.22(a).

Sec. 393.20 Clearance lamps to indicate extreme width and height.

Clearance lamps shall be mounted so as to indicate the extreme width
of the motor vehicle (not including mirrors) and as near the top thereof
as practicable: Provided, That when rear identification lamps are
mounted at the extreme height of the vehicle, rear clearance lamps may
be mounted at optional height: And provided further, That when mounting
of front clearance lamps at the highest point of a trailer results in
such lamps failing to mark the extreme width of the trailer, such lamps
may be mounted at optional height but must indicate the extreme width of
the trailer. Clearance lamps on truck tractors shall be so located as to
indicate the extreme width of the truck tractor cab.

Sec. 393.22 Combination of lighting devices and reflectors.

(a) Permitted combinations. Except as provided in paragraph (b) of
this section, two or more lighting devices and reflectors (whether or
not required by the rules in this part) may be combined optically if--

(1) Each required lighting device and reflector conforms to the
applicable rules in this part; and

(2) Neither the mounting nor the use of a nonrequired lighting
device or reflector impairs the effectiveness of a required lighting
device or reflector or causes that device or reflector to be
inconsistent with the applicable rules in this part.

(b) Prohibited combinations. (1) A turn signal lamp must not be
combined optically with either a head lamp or other lighting device or
combination of lighting devices that produces a greater intensity of
light than the turn signal lamp.

(2) A turn signal lamp must not be combined optically with a stop
lamp unless the stop lamp function is always deactivated when the turn
signal function is activated.

(3) A clearance lamp must not be combined optically with a tail lamp
or identification lamp.

Sec. 393.23 Lighting devices to be electric.

Lighting devices shall be electric, except that red liquid-burning
lanterns may be used on the end of loads in the nature of poles, pipes,
and ladders projecting to the rear of the motor vehicle.

Sec. 393.24 Requirements for head lamps and auxiliary road lighting lamps.

(a) Mounting. Head lamps and auxiliary road lighting lamps shall be
mounted so that the beams are readily adjustable, both vertically and
horizontally, and the mounting shall be such that the aim is not readily
disturbed by ordinary conditions of service.

(b) Head lamps required. Every bus, truck, and truck tractor shall
be equipped with a headlighting system composed of at least two head
lamps, not including fog or other auxiliary lamps, with an equal number
on each side of the vehicle. The headlighting system shall provide an
upper and lower distribution of light, selectable at the driver's will.

(c) Fog, adverse-weather, and auxiliary road-lighting lamps. For the
purposes of this section, fog, adverse-weather, and auxiliary road
lighting lamps, when installed, are considered to be a part of the
headlighting system. Such lamps may be used in lieu of head lamps under
conditions making their use advisable if there be at least one such lamp
conforming to the appropriate SAE Standard \1\ for such lamps on each
side of the vehicle.
---------------------------------------------------------------------------

\1\ Wherever reference is made in these regulations to SAE Standards
or SAE Recommended Practices, they shall be:

(a) As found in the 1985 edition of the SAE Handbook with respect to
parts and accessories other than lighting devices and reflectors.

(b) When reference is made in these regulations to SAE Standards or
SAE Recommended Practices, they shall be as found in the 1985 edition of
the SAE Handbook:

(1) With respect to parts and accessories other than lighting
devices and reflectors:

(2) Lighting devices and reflectors on motor vehicles manufactured
on and after March 7, 1990, shall conform to FMVSS 571.108 (49 CFR
571.108) in effect at the time of manufacture of the vehicle. Should a
conflict arise between FMVSS 571.108 and a SAE Standard, FMVSS 571.108
will prevail.
---------------------------------------------------------------------------

(d) Aiming and intensity. Head lamps shall be constructed and
installed so as to provide adequate and reliable illumination and shall
conform to the appropriate specification set forth in the SAE Standards
\1\ for ``Electric Head Lamps for Motor Vehicles'' or ``Sealed-Beam Head
Lamp Units for Motor Vehicles.''

Sec. 393.25 Requirements for lamps other than head lamps.

(a) Mounting. All lamps shall be permanently and securely mounted in
workmanlike manner on a permanent part of the motor vehicle, except that
temporary lamps on motor vehicles being transported in driveaway-towaway
operations and temporary electric lamps on projecting loads need not be
permanently mounted nor mounted on a permanent part of the vehicle. The
requirement for three identification lamps on the centerline of a
vehicle will be met as to location by one lamp on the centerline, with
the other two at right and left. All temporary lamps must be firmly
attached.

(b) Visibility. All required exterior lamps shall be so mounted as
to be capable of being seen at all distances between 500 feet and 50
feet under clear atmospheric conditions during the time lamps are
required to be lighted. The light from front clearance and front
identification lamps shall be visible to the front, that from sidemarker
lamps to the side, that from rear clearance, rear identification, and
tail lamps to the rear, and that from projecting loadmarker lamps from
those directions required by Sec. 393.11. This shall not be construed to
apply to lamps on one unit which are obscured by another unit of a
combination of vehicles.

(c) Specifications. All required lamps except those already
installed on vehicles tendered for transportation in 
driveaway and towaway operations shall conform to appropriate
requirements of the SAE Standards and/or Recommended Practices \1\ as
indicated below, except that the minimum required marking of lamps
conforming to the 1985 requirements shall be as specified in paragraph
(d) of this section. Projecting load marker lamps shall conform to the
requirements for clearance, side-marker, and identification lamps. Turn
signals shall conform to the requirements for class A, Type I turn
signals, provided.
---------------------------------------------------------------------------

\1\ See footnote 1 to Sec. 393.24(c).
---------------------------------------------------------------------------

(1) Lamps on vehicles made before July 1, 1961, excepting
replacement lamps as specified in paragraph (c)(2) of this section,
shall conform to the 1952 requirements.

(2) Lamps on vehicles made on and after July 1, 1961, and
replacement lamps installed on and after December 31, 1961, shall
conform to the 1985 requirements.

(3) Lamps temporarily attached to vehicles transported in driveaway
and towaway operations on and after December 31, 1961, shall conform to
the 1985 requirements.

(d) Certification and markings. All lamps required to conform to the
requirements of the SAE Standards \1\ shall be certified by the
manufacturer or supplier that they do so conform, by markings indicated
below. The markings in each case shall be visible when the lamp is in
place on the vehicle.
---------------------------------------------------------------------------

\1\ See footnote 1 to Sec. 393.24(c).
---------------------------------------------------------------------------

(1) Stop lamps shall be marked with the manufacturer's or supplier's
name or trade name and shall be marked ``SAE-S''.

(2) Turn signal units shall be marked with the manufacturer's or
supplier's name or trade name and shall be marked ``SAE-AI'' or ``SAE-
I''.

(3) Tail lamps shall be marked with the manufacturer's or supplier's
name or trade name and shall be marked ``SAE-T''.

(4) Clearance, side marker, identification, and projecting load-
marker lamps, except combination lamps, shall be marked with the
manufacturer's or supplier's name or trade name and shall be marked
``SAE'' or ``SAE-P''.

(5) Combination lamps shall be marked with the manufacturer's or
supplier's name or trade name and shall be marked ``SAE'' followed by
the appropriate letters indicating the individual lamps combined. The
letter ``A'', as specified in Sec. 393.26(c), may be included to certify
that a reflector in the combination conforms to the requirements
appropriate to such marking. If the letter ``I'' follows the letter
``A'' immediately the two letters shall be deemed to refer to a turn
signal unit, as specified in paragraph (d)(2) of this section.
Combination clearance and side marker lamps may be marked ``SAE-PC''.

(e) Lighting devices to be steady-burning. All exterior lighting
devices shall be of the steady-burning type except turn signals on any
vehicle, stop lamps when used as turn signals, warning lamps on school
buses when operating as such, and warning lamps on emergency and service
vehicles authorized by State or local authorities, and except that lamps
combined into the same shell or housing with any turn signal may be
turned off by the same switch that turns the signal on for flashing and
turned on again when the turn signal as such is turned off. This
paragraph shall not be construed to prohibit the use of vehicular hazard
warning signal flashers as required by Sec. 392.22 or permitted by
Sec. 392.18.

(f) Stop lamp operation. All stop lamps on each motor vehicle or
combination of motor vehicles shall be actuated upon application of any
of the service brakes, except that such actuation is not required upon
activation of the emergency feature of trailer brakes by means of either
manual or automatic control on the towing vehicle, and except that stop
lamps on a towing vehicle need not be actuated when service brakes are
applied to the towed vehicles or vehicles only, and except that no stop
lamp need be actuated as such when it is in use as a turn signal or when
it is turned off by the turn signal switch as provided in paragraph (e)
of this section.

Sec. 393.26 Requirements for reflectors.

(a) Mounting. All required reflectors shall be mounted upon the
motor vehicle at a height not less than 15 inches nor more than 60
inches above the ground on which the motor vehicle stands, except that
reflectors shall be mounted as high as practicable on motor vehicles
which are so constructed as to make compliance with the 15-inch
requirement impractical. They shall be so installed as to perform their
function adequately and reliably, and except for temporary reflectors
required for vehicles in driveaway-towaway operations, or on projecting
loads, all reflectors shall be permanently and securely mounted in
workmanlike manner so as to provide the maximum of stability and the
minimum likelihood of damage. Required reflectors otherwise properly
mounted may be securely installed on flexible strapping or belting
provided that under conditions of normal operation they reflect light in
the required directions. Required temporary reflectors mounted on motor
vehicles during the time they are in transit in any driveaway-towaway
operation must be firmly attached.

(b) Specifications. All required reflectors except those installed
on vehicles tendered for transportation in driveaway and towaway
operations shall comply with FMVSS 571.108 (49 CFR 571.108) in effect at
the time the vehicle was manufactured or the current FMVSS 571.108
requirements.

(c) Certification and markings. All reflectors required to conform
to the specifications in paragraph (b) shall be certified by the
manufacturer or supplier that they do so conform, by marking with the
manufacturer's or supplier's name or trade name and the letters ``SAE-
A''. The marking in each case shall be visible when the reflector is in
place on the vehicle.

(d) Retroreflective surfaces. Retroreflective surfaces other than
required reflectors may be used, provided:

(1) Designs do not resemble traffic control signs, lights, or
devices, except that straight edge striping resembling a barricade
pattern may be used.

(2) Designs do not tend to distort the length and/or width of the
motor vehicle.

(3) Such surfaces shall be at least 3 inches from any required lamp
or reflector unless of the same color as such lamp or reflector.

(4) No red color shall be used on the front of any motor vehicle,
except for display of markings or placards required by Sec. 177.823 of
this title.

(5) Retroreflective license plates required by State or local
authorities may be used.

Sec. 393.27 Wiring specifications.

(a) Wiring for both low voltage (tension) and high voltage (tension)
circuits shall be constructed and installed so as to meet design
requirements. Wiring shall meet or exceed, both mechanically and
electrically, the following SAE Standards as found in the 1985 edition
of the SAE Handbook:

(1) Commercial vehicle engine ignition systems-SAE J557-High Tension
Ignition Cable.

(2) Commercial vehicle battery cable-SAE J1127-Jan 80-Battery Cable.

(3) Other commercial vehicle wiring-SAE J1128-Low Tension Primary
Cable.

(b) The source of power and the electrical wiring shall be of such
size and characteristics as to provide the necessary voltage as the
design requires to comply with FMVSS 571.108.

(c) Lamps shall be properly grounded.

Sec. 393.28 Wiring to be protected.

(a) The wiring shall--

(1) Be so installed that connections are protected from weather,
abrasion, road splash, grease, oil, fuel and chafing;

(2) Be grouped together, when possible, and protected by
nonconductive tape, braid, or other covering capable of withstanding
severe abrasion or shall be protected by being enclosed in a sheath or
tube;

(3) Be properly supported in a manner to prevent chafing;

(4) Not be so located as to be likely to be charred, overheated, or
enmeshed in moving parts;

(5) Not have terminals or splices located above the fuel tank except
for the fuel sender wiring and terminal; and

(6) Be protected when passing through holes in metal by a grommet,
or other means, or the wiring shall be encased in a protective covering.

(b) The complete wiring system including lamps, junction boxes,
receptacle boxes, conduit and fittings must be weather resistant.

(c) Harness connections shall be accomplished by a mechanical means.

Sec. 393.29 Grounds.

The battery ground and trailer return ground connections on a
grounded system shall be readily accessible. The contact surfaces of
electrical connections shall be clean and free of oxide, paint, or other
nonconductive coating.

Sec. 393.30 Battery installation.

Every storage battery on every vehicle, unless located in the engine
compartment, shall be covered by a fixed part of the motor vehicle or
protected by a removable cover or enclosure. Removable covers or
enclosures shall be substantial and shall be securely latched or
fastened. The storage battery compartment and adjacent metal parts which
might corrode by reason of battery leakage shall be painted or coated
with an acid-resisting paint or coating and shall have openings to
provide ample battery ventilation and drainage. Wherever the cable to
the starting motor passes through a metal compartment, the cable shall
be protected against grounding by an acid and waterproof insulating
bushing. Wherever a battery and a fuel tank are both placed under the
driver's seat, they shall be partitioned from each other, and each
compartment shall be provided with an independent cover, ventilation,
and drainage.

Sec. 393.31 Overload protective devices.

(a) The current to all low tension circuits shall pass through
overload protective devices except that this requirement shall not be
applicable to battery-to-starting motor or battery-to-generator
circuits, ignition and engine control circuits, horn circuits,
electrically-operated fuel pump circuits, or electric brake circuits.

(b) Trucks, truck-tractors, and buses meeting the definition of a
commercial motor vehicle and manufactured after June 30, 1953 shall have
protective devices for electrical circuits arranged so that:

(1) The headlamp circuit or circuits shall not be affected by a
short circuit in any other lighting circuits on the motor vehicle; or

(2) The protective device shall be an automatic reset overload
circuit breaker if the headlight circuit is protected in common with
other circuits.

Sec. 393.32 Detachable electrical connections.

Electrical wiring between towing and towed vehicles shall be
contained in a cable or cables or entirely within another substantially
constructed protective device. All such electrical wiring shall be
mechanically and electrically adequate and free of short or open
circuits. Suitable provision shall be made in every such detachable
connection to afford reasonable assurance against connection in an
incorrect manner or accidental disconnection. Detachable connections
made by twisting together wires from the towed and towing units are
prohibited. Precaution shall be taken to provide sufficient slack in the
connecting wire or cable to accommodate without damage all normal
motions of the parts to which they are attached.

Sec. 393.33 Wiring, installation.

Electrical wiring shall be systematically arranged and installed in
a workmanlike manner. All detachable wiring, except temporary wiring
connections for driveaway-towaway operations, shall be attached to posts
or terminals by means of suitable cable terminals which conform to the 
SAE Standard \1\ for ``Cable Terminals'' or by cable terminals which are 
mechanically and electrically at least equal to such terminals. The number 
of wires attached to any post shallbe limited to the number which such post 
was designed to accommodate. The presence of bare, loose, dangling, 
chafing, or poorly connected wires is prohibited.

Sec. 393.40 Required brake systems.

(a) General. A bus, truck, truck tractor, or a combination of motor
vehicles must have brakes adequate to control the movement of, and to
stop and hold, the vehicle or combination of vehicles.

(b) Specific systems required. (1) A bus, truck, truck tractor, or
combination of motor vehicles must have--

(i) A service brake system that conforms to the requirements of
Sec. 393.52; and

(ii) A parking brake system that conforms to the requirements of
Sec. 393.41.

(2) A bus, truck, truck tractor, or a combination of motor vehicles
manufactured on or after July 1, 1973, must have an emergency brake
system that conforms to the requirements of Sec. 393.52(b) and consists
of either--

(i) Emergency features of the service brake system; or

(ii) A system separate from the service brake system.

A control by which the driver applies the emergency brake system must be
located so that the driver can readily operate it when he/she is
properly restrained by any seat belt assembly provided for his/her use.
The control for applying the emergency brake system may be combined with
either the control for applying the service brake system or the control
for applying the parking brake system. However, all three controls may
not be combined.

(c) Interconnected systems. (1) If the brake systems specified in
paragraph (b) of this section are interconnected in any way, they must
be designed, constructed, and maintained so that, upon the failure of
any part of the operating mechanism of one or more of the systems
(except the service brake actuation pedal or valve)--

(i) The vehicle will have operative brakes; and

(ii) In the case of a vehicle manufactured on or after July 1, 1973,
the vehicle will have operative brakes capable of performing as
specified in Sec. 393.52(b).

(2) A motor vehicle to which the emergency brake system requirements
of Federal Motor Vehicle Safety Standard No. 105 (Sec. 571.105 of this
title) applied at the time of its manufacture conforms to the
requirements of paragraph (c)(1) of this section if--

(i) It is maintained in conformity with the emergency brake
requirements of Standard No. 105 in effect on the date of its
manufacture; and

(ii) It is capable of performing as specified in Sec. 393.52(b),
except upon structural failure of its brake master cylinder body or
effectiveness indicator body.

(3) A bus conforms to the requirements of paragraph (c)(1) of this
section if it meets the requirements of Sec. 393.44 and is capable of
performing as specified in Sec. 393.52(b).

Sec. 393.41 Parking brake system.

(a) Every commercial motor vehicle manufactured on and after March
7, 1990, except an agricultural commodity trailer, converter dolly,
heavy hauler or pulpwood trailer, shall at all times be equipped with a
parking brake system adequate to hold the vehicle or combination under
any condition of loading as required by FMVSS 571.121. An agricultural
commodity trailer, heavy hauler or pulpwood trailer shall carry
sufficient chocking blocks to prevent movement when parked.

(b) The parking brake system shall at all times be capable of being
applied in conformance with the requirements of paragraph (a) of the
section by either the driver's muscular effort, or by spring action, or
by other energy, provided, that if such other energy is depended on for
application of the parking brake, then an accumulation of such energy
shall be isolated from any common source and used exclusively for the
operation of the parking brake.

(c) The parking brake system shall be held in the applied position
by energy other than fluid pressure, air pressure, or electric energy.
The parking brake system shall be such that it cannot be released unless
adequate energy is available upon release of the parking brake to make
immediate further application with the required effectiveness.

Sec. 393.42 Brakes required on all wheels.

(a) Every commercial motor vehicle shall be equipped with brakes
acting on all wheels.

(b) Exception. (1) Trucks or truck tractors having three or more
axles--

(i) Need not have brakes on the front wheels if the vehicle was
manufactured before July 25, 1980; or

(ii) Manufactured between July 24, 1980, and October 27, 1986, must
be retrofitted to meet the requirements of this section within one year
from February 26, 1987, if the brake components have been removed.

(2) Any motor vehicle being towed in a driveaway-towaway operation
must have operative brakes as may be necessary to ensure compliance with
the performance requirements of Sec. 393.52. This paragraph is not
applicable to any motor vehicle towed by means of a tow-bar when any
other vehicle is full-mounted on such towed motor vehicle or any
combination of motor vehicles utilizing three or more saddle-mounts.
(See Sec. 393.71(a)(3).)

(3) Any full trailer, any semitrailer, or any pole trailer having a
GVWR of 3,000 pounds or less must be equipped with brakes if the weight
of the towed vehicle resting on the towing vehicle exceeds 40 percent of
the GVWR of the towing vehicle.

Sec. 393.43 Breakaway and emergency braking.

(a) Every motor vehicle, if used to tow a trailer equipped with
brakes, shall be equipped with means for providing that in case of
breakaway of such trailer the service brakes on the towing vehicle will
be sufficiently operative to stop the towing vehicle.

(b) Every truck or truck tractor equipped with air brakes, when used
for towing other vehicles equipped with air brakes, shall be equipped
with two means of activating the emergency features of the trailer
brakes. One of these means shall operate automatically in the event of
reduction of the towing vehicle air supply to a fixed pressure which
shall not be lower than 20 pounds per square inch nor higher than 45
pounds per square inch. The other means shall be a manually controlled
device readily operable by a person seated in the driving seat. Its
emergency position or method of operation shall be clearly indicated. In
no instance may the manual means be so arranged as to permit its use to
prevent operation of the automatic means. The automatic and manual means
required by this section may be, but are not required to be, separate.

(c) Every truck tractor and truck when used for towing other
vehicles equipped with vacuum brakes, shall have, in addition to the
single control required by Sec. 393.49 to operate all brakes of the
combination, a second manual control device which can be used
to operate the brakes on the towed vehicles in emergencies. Such 
second control shall be independent of brake air, hydraulic, and other 
pressure, and independent of other controls, unless the braking system 
be so arranged that failure of the pressure on which the second control 
depends will cause the towed vehicle brakes to be applied automatically. 
The second control is not required by this rule to provide modulated or 
graduated braking.

(d) Every trailer required to be equipped with brakes shall be
equipped with brakes of such character as to be applied automatically
and promptly upon breakaway from the towing vehicle, and means shall be
provided to maintain application of the brakes on the trailer in such
case for at least 15 minutes.

(e) Air brake systems installed on towed vehicles shall be so
designed, by the use of ``no-bleed-back'' relay emergency valves or
equivalent devices, that the supply reservoir used to provide air for
brakes shall be safeguarded against backflow of air to the towing
vehicle upon reduction of the towing vehicle air pressure.

(f) The requirements of paragraphs (b), (c), and (d) of this section
shall not be applicable to motor vehicles in driveaway-towaway
operations.

Sec. 393.44 Front brake lines, protection.

On every bus, if equipped with air brakes, the braking system shall
be so constructed that in the event any brake line to any of the front
wheels is broken, the driver can apply the brakes on the rear wheels
despite such breakage. The means used to apply the brakes may be located
forward of the driver's seat as long as it can be operated manually by
the driver when the driver is properly restrained by any seat belt
assembly provided for use. Every bus shall meet this requirement or
comply with the regulations in effect at the time of its manufacture.

Sec. 393.45 Brake tubing and hose, adequacy.

(a) General requirements. Brake tubing and brake hose must--

(1) Be designed and constructed in a manner that insures proper,
adequate, and continued functioning of the tubing or hose;

(2) Be installed in a manner that insures proper continued
functioning of the tubing or hose;

(3) Be long and flexible enough to accommodate without damage all
normal motions of the parts to which it is attached;

(4) Be suitably secured against chafing, kinking, or other
mechanical damage;

(5) Be installed in a manner that prevents it from contacting the
vehicle's exhaust system or any other source of high temperatures; and

(6) Conform to the applicable requirements of paragraph (b) or (c)
of this section. In addition, all hose installed on and after January 1,
1981, must conform to those applicable subsections of FMVSS 106 (49 CFR
571.106).

(b) Special requirements for metallic brake tubing, nonmetallic
brake tubing, coiled nonmetallic brake tubing and brake hose. (1)
Metallic brake tubing, nonmetallic brake tubing, coiled nonmetallic
brake tubing, and brake hose installed on a commercial motor vehicle on
and after March 7, 1989, must meet or exceed one of the following
specifications set forth in the SAE Handbook, 1985 edition:

(i) Metallic Air Brake Tubing--SAE Recommended Practice J1149--
Metallic Air Brake System Tubing and Pipe--July 76.

(ii) Nonmetallic Air Brake Tubing--SAE Recommended Practice J844--
Nonmetallic Air Brake System Type B--OCT 80.

(iii) Air Brake Hose--SAE Recommended Practice J1402--Automotive Air
Brake Hose and Hose Assemblies--JUN 85.

(iv) Hydraulic Brake Hose--SAE Recommended Practice J1401 Road
Vehicle-Hydraulic Brake Hose Assemblies for Use with Non-Petroleum Base
Hydraulic Fluid JUN 85.

(v) Vacuum Brake Hose--SAE Recommended Practice J1403 Vacuum Brake
Hose JUN 85.

(2) Except as provided in paragraph (c) of this section, brake hose
and brake tubing installed on a motor vehicle before March 7, 1989, must
conform to 49 CFR 393.45 effective October 31, 1983.

(c) Nonmetallic brake tubing. Coiled nonmetallic brake tubing may be
used for connections between towed and towing vehicles or between the
frame of a towed vehicle and the unsprung subframe of an adjustable axle
of that vehicle if--

(1) The coiled tubing has a straight segment (pigtail) at each end
that is at least 2 inches in length and is encased in a spring guard or
similar device which prevents the tubing from kinking at the fitting at
which it is attached to the vehicle; and

(2) The spring guard or similar device has at least 2 inches of
closed coils or similar surface at its interface with the fitting and
extends at least 1\1/2\ inches into the coiled segment of the tubing
from its straight segment.

(d) Brake tubing and brake hose, uses. Metallic and nonmetallic
brake tubing is intended for use in areas of the brake system where
relative movement in the line is not anticipated. Brake hose and coiled
nonmetallic brake tubing is intended for use in the brake system where
substantial relative movement in the line is anticipated or the hose/
coiled nonmetallic brake tubing is exposed to potential tension or
impact such as between the frame and axle in a conventional type
suspension system (axle attached to frame by suspension system).
Nonmetallic brake tubing may be used through an articulation point
provided movement is less than 4.5 degrees in a vertical plane, and 7.4
degrees in a transverse horizontal plane.

Sec. 393.46 Brake tubing and hose connections.

All connections for air, vacuum, or hydraulic braking systems shall:

(a) Be adequate in material and construction to insure proper
continued functioning;

(b) Be designed, constructed, and installed so as to insure, when
properly connected, an attachment free of leaks, constrictions, or other
defects;

(c) Have suitable provision in every detachable connection to afford
reasonable assurance against accidental disconnection;

(d) Have the vacuum brake engine manifold connection at least three-
eighths inch in diameter.

(e) If installed on a vehicle on or after January 1, 1981, meet
requirements under applicable subsections of FMVSS 106 (49 CFR 571.106).

(f) Splices in tubing if installed on a vehicle after March 7, 1989,
must use fittings that meet the requirements of SAE Standard J512-OCT 80
Automotive Tube Fittings or for air brake systems SAE J246--March 81
Spherical and Flanged Sleeve (Compression) Tube Fittings as found in the
SAE Handbook 1985 edition.

Sec. 393.47 Brake lining.

The brake lining in every motor vehicle shall be so constructed and
installed as not to be subject to excessive fading and grabbing and
shall be adequate in thickness, means of attachment, and physical
characteristics to provide for safe and reliable stopping of the motor
vehicle.

Sec. 393.48 Brakes to be operative.

(a) General rule. Except as provided in paragraphs (b) and (c) of
this section, all brakes with which a motor vehicle is equipped must at
all times be capable of operating.

(b) Devices to reduce or remove front-wheel braking effort. A motor
vehicle may be equipped with a device to reduce the braking effort upon
its front wheels or, in the case of a three-axle truck or truck tractor
manufactured before March 1, 1975, to remove the braking effort upon its
front wheels, if that device conforms to, and is used in compliance
with, the rules in paragraph (b) (1) or (2) of this section.

(1) Manually operated devices. A manually operated device to reduce
or remove the front-wheel braking effort must not be--

(i) Installed in a motor vehicle other than a bus, truck, or truck
tractor; or

(ii) Installed in a bus, truck, or truck tractor manufactured after
February 28, 1975; or

(iii) Used in the reduced mode except when the vehicle is operating
under adverse conditions such as wet, snowy, or icy roads.

(2) Automatic devices. An automatic device to reduce the front-wheel
braking effort by up to 50 percent of the normal braking force,
regardless of whether or not antilock system failure has occurred on any
axle, must not--

(i) Be operable by the driver except upon application of the control
that activates the braking system; and

(ii) Be operable when the pressure that transmits brake control
application force exceeds--

(A) 85 psig on air-mechanical braking systems; or

(B) 85 percent of the maximum system pressure in the case of
vehicles utilizing other than compressed air.

(c) Towed vehicle. Paragraph (a) of this section does not apply to--

(1) A disabled vehicle being towed; or

(2) A vehicle being towed in a driveaway-towaway operation which is
exempt from the general rule of Sec. 393.42 under paragraph (b) of that
section.

Sec. 393.49 Single valve to operate all brakes.

Every motor vehicle, the date of manufacture of which is subsequent
to June 30, 1953, which is equipped with power brakes, shall have the
braking system so arranged that one application valve shall when applied
operate all the service brakes on the motor vehicle or combination of
motor vehicles. This requirement shall not be construed to prohibit
motor vehicles from being equipped with an additional valve to be used
to operate the brakes on a trailer or trailers or as provided in
Sec. 393.44. This section shall not be applicable to driveaway-towaway
operations unless the brakes on such operations are designed to be
operated by a single valve.

Sec. 393.50 Reservoirs required.

(a) General. Every commercial motor vehicle using air or vacuum for
breaking shall be equipped with reserve capacity or a reservoir
sufficient to ensure a full service brake application with the engine
stopped without depleting the air pressure or vacuum below 70 percent of
that pressure or degree of vacuum indicated by the gauge immediately
before the brake application is made. For purposes of this section, a
full service brake application is considered to be made when the service
brake pedal is pushed to the limit of its travel.

(b) Safeguarding of air and vacuum. (1) Every bus, truck, and truck
tractor, when equipped with air or vacuum reservoirs and regardless of
date of manufacture, shall have such reservoirs so safeguarded by a
check valve or equivalent device that in the event of failure or leakage
in its connection to the source of compressed air or vacuum the air or
vacuum supply in the reservoir shall not be depleted by the leak or
failure.