APPENDIX 4.2–SPECIFICATION FOR AN AUTOMATIC BRAKING SYSTEM
SCOPE
A4.2.1 This is a generic specification for systems intended to apply the brakes of a heavy goods motor vehicle (HGV) in the event of a collision from the rear.
A4.2.2 This specification only applies when the said system is fitted to a vehicle being employed for the purpose of acting as an Impact Protection Vehicle (IPV) or block vehicle for a Mobile Lane Closure.
A4.2.3 The fitment of all such devices requires a “Notifiable Alteration” to be recorded with the Vehicle and Operator Services Agency.
A4.2.4 All such systems first fitted on or after the 1st June 2003 shall meet the requirements contained herein.
PURPOSE
A4.2.5 The purpose of this specification is to ensure that automatic impact braking systems meet certain minimum performance standards and have no deleterious effect on the operation of the standard service, secondary and parking brake systems. It is not intended to be a comprehensive design specification. Manufacturers shall design their system and its components within the constraints contained in this specification.
OPERATIONAL REQUIREMENTS
A4.2.6 The impact braking system shall be energised by a driver-operated control but it shall only be capable of functioning when the control is in the on position and the crash cushion has been lowered.
A4.2.7 If the driver-operated control is in the on position, the impact braking system shall be automatically enabled when the crash cushion is lowered. Conversely, raising the crash cushion shall automatically disable the impact braking system.
A4.2.8 The system shall incorporate one of the two following facilities:
- a diagnostic self-test function capable of detecting system defects and warning the driver; or
- a manual test facility allowing an operator to check for the correct function of the system. This test should be sufficiently simple to be incorporated into routine daily maintenance schedules.
A4.2.9 If a collision is detected the brakes shall be applied to all wheels of the vehicle.
A4.2.10 If the system has been activated, it shall continue to apply the vehicle brakes until such time as it is reset by switching it off at a control specifically designed and marked for the purpose. It shall not be possible to reset the impact braking system unless the parking brake has been applied.
DESIGN AND INSTALLATION REQUIREMENTS
A4.2.11 The system shall be designed and installed in such a way that it has no effect on the normal operation of the service, secondary and parking brake systems.
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