Appendix BRearward seat collapse#
Prevention of rearward seat collapse#
Background#
The Queensland Department of Transport and Main Roads experienced a TMA incident where the driver’s seat failed in a rearward direction. The driver’s head hit the rear of the cabin and the driver also suffered back injuries, which have permanently prevented his return to work.
Rearward seat collapse#
The purpose of this requirement is to reduce the likelihood of rearward seat collapse in the event of a substantial impact to the rear of a TMA. This will reduce the likelihood of injury to a TMA occupant.
The purpose of this requirement may be achieved by either of two methods:
- 1.By design or testing, determine that the seat and mountings are of sufficient strength to withstand, in the rearward direction, similar loading to that applied to the seat and seat mountings in a forward direction for ADR compliance.
- 2.By fitting a device behind the seat to restrict rearward seat collapse when the same loadings are applied in a rearward direction.
The rearward loading requirements are based on ADR 5/05 requirements.
ADR 5/05 relates to seat belt anchorage strength required to restrain an occupant in a frontal impact. In a rear impact, the seat belt has no effect and rearward movement of the occupant is restrained by the seat structure and seat mountings only.
The TMA requirement is intended to afford a seat occupant a similar level of protection in the event of a rear impact that the ADRs provide in a frontal impact.
ADR 5/05 requires that, for heavy goods vehicles (GVM >12 t) with lap belt anchorages located wholly within the seat structure, the seat and the belt anchorages must withstand the following loading in the forward direction:
A test load of 740 ± 20 daN supplemented by a force equal to 6.6 times the mass of the complete seat.
The TMA requirement imposes the same loading in a rearward direction to simulate the effects of a rear impact.
Evidence of compliance with these rearward loading requirements can be either by design verification or by representative test results. This evidence would give blanket cover (type approval) to that seat / vehicle combination and the vehicle / seat supplier or verifying engineer would supply certification of same.
If evidence of compliance with additional rearward loading requirements is not available, a device to prevent rearward seat collapse would be fitted.
Given this requirement, and that the seat assembly is certified to withstand applied loads in a forward direction, the original equipment seats may meet the TMA requirements.
