Proposal to amend para. 2.8 of Annex 8 to add a new requirement that braking forces from combined service and parking braking systems shall hold a laden trailer as required in Annex 4 para. 3.2.1 at any time when service brake energy reservoir pressure reduces from 850 kPa to 0 kPa, ensuring continuous trailer immobilisation during service brake pressure depletion while establishing a performance-based requirement rather than prescribing specific technical solutions.

Proposal to amend Annex 8, paragraph 2.8. to establish performance-based requirements ensuring continuous trailer immobilisation during service brake pressure depletion. The amendment requires that when a trailer is uncoupled and the park brake control is released, braking forces from combined service and parking braking systems shall hold the laden trailer at any time when service brake energy reservoir reduces from 850 kPa to 0 kPa, and that adequate overlap between service brake and spring brake functions be ensured so no loss of holding capability occurs during pressure depletion.

In January 2022, an M₁ passenger vehicle with a detached tyre caused its Anti-lock Braking System to activate, preventing effective braking and resulting in collision with a stationary lorry. The coroner concluded the ABS functioned as intended but created an unsafe scenario by using the fastest rotating wheel as reference speed, and recommended changes to prevent future deaths. The UK proposal to amend UN R13-H would require manufacturers to affirm that strategies to achieve system objectives will not prejudice safe operation of systems under non-fault conditions, including failures of other systems involved in achieving system function such as tyres or wheels, and that documentation be supported by analysis showing how the system will behave upon any fault with bearing on vehicle control, performance, or safety, including faults with other systems involved in achieving system function.

Proposal to amend Annex 8, para. 3.4.1. to require that the strategy chosen shall not prejudice safe operation of the system due to failures with other systems involved in achieving the function of the system, and amend Annex 8, para. 3.4.4. to require that analysis of system behaviour on fault occurrence includes faults with other systems involved in achieving the function of the system, and to correct ‘safetys’ to ‘safety’. The proposal addresses a collision where tyre failure resulted in unsafe ABS activation. Although the 02 series clarified ABS as part of electronic control systems assessment, it does not explicitly state what is covered, potentially missing relevant faults or failures influencing system function. The additions ensure all relevant faults or failures are accounted for in manufacturers’ safety concept and analysis.

Proposal to amend para. 3.4.1. and para. 3.4.4. in Annex 8 to require manufacturers to address how the braking system strategy will not prejudice safe operation due to failures with other systems involved in achieving the function of the system, and insert new para. 4.5. in Annex 6 to require consideration of the effect of implausible wheel-speed information on anti-lock system operation in fault analysis. The proposal responds to a United Kingdom collision involving tyre failure and ABS activation that resulted in unsafe operation.

Proposal to amend para. 3.4.1. and 3.4.4. of Annex 8 to require manufacturers to account for faults or failures with other systems involved in achieving the function of the braking system in their safety concept and analysis, and insert new para. 4.5. in Annex 6 requiring consideration of implausible wheel-speed information effects on anti-lock system operation in fault analysis. The proposal responds to a fatal collision in the United Kingdom where tyre failure and inaccurate wheel speed signals caused ABS activation that resulted in loss of braking force.