26502.  (a) Airbrakes of every motor vehicle and combination of
vehicles shall be so adjusted and maintained as to be capable of
providing full service brake application at all times except as
provided in subdivision (b) of Section 26311.  A full service brake
application shall deliver to all brake chambers not less than 90
percent of the air reservoir pressure remaining with the brakes
applied.
   (b) The department may by regulation authorize the use of special
devices or systems to automatically reduce the maximum air pressure
delivered to the brake chambers in order to compensate for load
variation and to obtain balanced braking.  Permitted systems shall be
of the fail safe type and shall not increase the vehicle stopping
distance.



26503.  Every motor vehicle equipped with airbrakes or equipped to
operate airbrakes on towed vehicles shall be equipped with a standard
type safety valve which shall be installed so as to have an
uninterrupted connection with the air reservoir or tank.  It shall be
adjusted and maintained so that it will open and discharge the air
system under any condition at a pressure of not to exceed 150 pounds
per square inch and close and reseat itself at a point above the
maximum air governor setting.  The department may by regulation
prescribe a higher maximum opening pressure for air pressure systems
designed for, and capable of safely operating with, pressure safety
valves with a higher opening pressure.



26504.  The air governor cut-in and cut-out pressures of every motor
vehicle equipped with airbrakes or equipped to operate airbrakes on
towed vehicles shall be adjusted so that the maximum pressure in the
air system and the minimum cut-in pressure shall be within limits
prescribed by the department.  In adopting regulations specifying
such pressures the department shall consider the safe operating
capacities of the various airbrake systems which are now or may be
used on motor vehicles and shall be guided by the designed
capabilities of those systems.


26505.  Every motor vehicle equipped with airbrakes or equipped to
operate airbrakes on towed vehicles shall be equipped with a pressure
gauge of reliable and satisfactory construction and maintained in an
efficient working condition, accurate within 10 percent of the
actual air reservoir pressure, and visible and legible to the driver
at all times.



26506.  (a) Every motor vehicle airbrake system used to operate the
brakes on a motor vehicle or on a towed vehicle shall be equipped
with a low air pressure warning device that complies with either the
requirements set forth in the Federal Motor Vehicle Safety Standards
in effect at the time of manufacture or the requirements of
subdivision (b).
   (b) The device shall be readily visible or audible to the driver
and shall give a satisfactory continuous warning when the air supply
pressure drops below a fixed pressure, which shall be not more than
75 pounds per square inch nor less than 55 pounds per square inch
with the engine running.  A gauge indicating pressure shall not
satisfy this requirement.


26507.  A check valve shall be installed and properly maintained in
the air supply piping of every motor vehicle equipped with airbrakes,
either between the air compressor and the first reservoir or tank
immediately adjacent to the air intake of said reservoir, or between
No. 1 reservoir (wet tank) and No. 2 reservoir (dry tank) immediately
adjacent to the air intake of the No. 2 reservoir; provided, that
the air supply for the brakes is not drawn from the No. 1 reservoir
and that the No. 1 and No. 2 reservoirs are connected by only one
pipeline.


26508.  Every vehicle or combination of vehicles using compressed
air at the wheels for applying the service brakes shall be equipped
with an emergency stopping system meeting the requirements of this
section and capable of stopping the vehicle or combination of
vehicles in the event of failure in the service brake air system as
follows:
   (a) Every motor vehicle operated either singly or in a combination
of vehicles and every towed vehicle shall be equipped with an
emergency stopping system.
   (b) Motor vehicles used to tow vehicles which use compressed air
at the wheels for applying the service brakes shall be equipped with
a device or devices with both a manual and automatic means of
actuating the emergency stopping system on the towed vehicle as
follows:
   (1) The automatic device shall operate automatically in the event
of reduction of the service brake air supply of the towing vehicle to
a fixed pressure which shall be not lower than 20 pounds per square
inch nor higher than 45 pounds per square inch.
   (2) The manual device shall be readily operable by a person seated
in the driver's seat, with its emergency position or method of
operation clearly indicated.  In no instance may the manual means be
so arranged as to permit its use to prevent operation of the
automatic means.
   (c) Motor vehicles manufactured prior to 1964 shall be deemed to
be in compliance with subdivisions (e) and (f) when equipped with
axle-by-axle protected airbrakes using a separate air tank system for
each of at least two axles, provided that each system independently
meets all other requirements of this section.  Each system shall be
capable of being manually applied, released, and reapplied from the
driver's seat but shall not be capable of being released from the
driver's seat after any reapplication unless there is available a
means which can be applied from the driver's seat to stop and hold
the vehicle or combination of vehicles.
   (d) Towed vehicles shall be deemed to be in compliance with this
section when:
   (1) The towed vehicle is equipped with a no-bleed-back
relay-emergency valve or equivalent device, so designed that the
supply reservoir used to provide air for the brakes is safeguarded
against backflow of air from the reservoir through the supply line,
   (2) The brakes are applied automatically and promptly upon
breakaway from the towing vehicle and maintain application for at
least 15 minutes, and
   (3) The combination of vehicles is capable of stopping within the
distance and under the conditions specified in subdivisions (k) and
(l).
   (e) If the service brake system and the emergency stopping system
are connected in any way, they shall be so constructed that a failure
or malfunction in any one part of either system, including brake
chamber diaphragm failure but not including failure in the drums,
brakeshoes, or other mechanical parts of the wheel brake assemblies,
shall not leave the vehicle without one operative stopping system
capable of complying with the performance requirements in subdivision
(k).
   (f) Every emergency stopping system shall be designed so that it
is capable of being manually applied, released, and reapplied by a
person seated in the driver's seat.  The system shall be designed so
that it cannot be released from the driver's seat after any
reapplication unless immediate further application can be made from
the driver's seat to stop and hold the vehicle or combination of
vehicles.  The emergency stopping system may also be applied
automatically.
   (g) No vehicle or combination of vehicles upon failure of the
service brake air system shall be driven on a highway under its own
power except to the extent necessary to move the vehicles off the
roadway to the nearest place of safety.
   (h) No vehicle or combination of vehicles shall be equipped with
an emergency stopping system that creates a hazard on the highway, or
increases the service brake stopping distance of a vehicle or
combination of vehicles, or interferes in any way with the
application of the service brakes on any vehicle or combination of
vehicles.
   (i) Any energy-storing device which is a part of the emergency
stopping system shall be designed so that it is recharged or reset
from the course of compressed air or other energy produced by the
vehicle, except that energy to release the emergency stopping system
may be produced by the driver's muscular effort from the driver's
seat.  No device shall be used which can be set to prevent automatic
delivery of air to protected air supply reservoirs of motor vehicle
emergency stopping systems when air is available in the service brake
air supply system.
   (j) Any vehicle manufactured on or after January 1, 1964, which
uses axle-by-axle protected airbrakes as the emergency stopping
system shall use a separate air tank system for each axle, except
that motor vehicles equipped with a dual or tandem treadle valve
system need have no more than two protected air tanks in such system,
one for each valve.
   (k) Every motor vehicle or combination of vehicles, at all times
and under all conditions of loading, upon application of the
emergency stopping system, shall be capable of:
   (1) Developing a stopping force that is not less than the
percentage of its gross weight tabulated herein for its
classification.
   (2) Decelerating in a stop from 20 miles per hour at not less than
the feet per second per second tabulated herein for its
classification, and
   (3) Stopping from a speed of 20 miles per hour in not more than
the distance tabulated herein for its classification, such distance
to be measured from the point at which movement of the emergency
stopping system control begins.

      EMERGENCY STOPPING SYSTEM REQUIREMENTS


                             Stopping force
       Classification        as a percentage      Deceleration
       of vehicle            of gross vehicle       in feet
Stopping
       and combination        or combination       per second
distance
       of vehicles               weight            per second      in
feet
    A  Single-motor
       vehicles ................   16.7                5.5
  90
    B  Combination of
       vehicles ................   19.0                6.0
  90
    C  Single-motor
       vehicle with 3
       or more axles
       manufactured
       prior to 1964 ...........   12.1                4.0
120

   (l) Tests for deceleration and stopping distance shall be made on
a substantially level, dry, smooth, hard surface that is free from
loose material and where the grade does not exceed plus or minus 1
percent.  No test of emergency stopping system performance shall be
made upon a highway at a speed in excess of 25 miles per hour.
   (m) The provisions of this section shall not apply to:
   (1) Auxiliary dollies, special mobile equipment, or special
construction equipment.
   (2) Motor vehicles which are operated in a driveaway-towaway
operation and not registered in this state.
   (3) Disabled vehicles when being towed.
   (4) Vehicles which are operated under a one-trip permit as
provided in Section 4003.
   (5) Vehicles which because of unladen width, length, height or
weight may not be moved upon the highway without the permit specified
in Section 35780.
   (n) The emergency stopping system requirements specified in
subdivision (k) shall not apply to a vehicle or combination of
vehicles being operated under a special weight permit nor to any
overweight authorized emergency vehicle operated under the provisions
of Section 35002.
   (o) Every owner or lessee shall instruct and require that the
driver be thoroughly familiar with the requirements of this section.
The driver of a vehicle or combination of vehicles required to
comply with the requirements of this section shall be able to
demonstrate the application and release of the emergency system on
the vehicle and each vehicle in the combination.