Document ID: chunk:federal_register_of_legislation:F2018C00341:body:0:p10
Version: federal_register_of_legislation:F2018C00341
Segment Type: other
Provision Reference: 
Character Range: 28370–31484

'Control' of the 'Secondary Brake System' must be capable of releasing and applying the secondary brake after its first application.  The 'Control' must be so placed that it can be operated by the driver in the normal driving position.
4.5.5.                              A 'Secondary Brake System' may utilise elements of the 'Service Brake System'.
4.5.6.                              Where the 'Secondary Brake System' is a 'Spring Brake System':
4.5.6.1.                        in a single circuit 'Service Brake System', the energy supply system for maintaining the secondary brake in its released position must include a 'Stored Energy' device that does not service any other device or equipment;
4.5.6.2.                                      in the event of failure of the energy supply to any one circuit of a 'Service Brake System' employing two or more independent circuits, the energy requirements for retaining the secondary brakes in the released position must be supplied from the 'Stored Energy' device(s) of the other circuits or optionally from an independent 'Stored Energy' device; and
4.5.6.3.                                      with the 'Stored Energy' device charged to its 'Average Operating Pressure' it must have sufficient capacity to permit the 'Secondary Brake System' to be applied and released not fewer than:
         4.5.6.3.1.  Two (2) times when the brakes are adjusted so that the distance travelled by the device which directly actuates the brake shoe or pad is a maximum, or
         4.5.6.3.2.  Three (3) times when the brakes are adjusted to the 'Manufacturer' specifications.
4.5.7.                                            In a vehicle equipped with a 'Brake Power Assist Unit' normally supplied with high pressure fluid by an engine driven pump, a back-up system must be regarded as a 'Secondary Brake System' if the back up source of power assistance is immediately energized by a pump driven independently of the vehicle engine.
4.5.8.                                            Every motor vehicle equipped to tow a trailer must be so equipped that its brake system remains operative and has the performance of the Laden Secondary Brake Test (item 7 of Table 1) in the event of the trailer becoming disconnected. This protection must be automatic.
4.5.8.1.                        Protection systems may vent the trailer 'Supply Line 35/...' but this must not commence;
4.5.8.2.1.                  until the energy level in the 'Supply Line 35/...' falls below 0.54 'E' (350 kPa) or,
4.5.8.2.2.                  if the 'Supply Line 35/...' energy level is reducing at a rate of not less than 0.15E/sec (100 kPa/sec), until the energy level in the 'Supply Line 35/...' falls below 0.65 'E'(420 kPa).
4.5.9.                                            Every motor vehicle which provides its 'Secondary Braking System' by means of a 'Split Service Brake System' and which is equipped to tow a trailer which uses air at positive pressure, must be so equipped that the operation of the 'Secondary Brake System' causes a control signal proportional to the degree of braking