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Cover of Developing Braking Standards for Heavy Vehicles to Brake Effectively and Safely on Steep Declines
Developing Braking Standards for Heavy Vehicles to Brake Effectively and Safely on Steep Declines
  • Publication no: AP-R539-17
  • ISBN: 978-1-925451-59-7
  • Published: 10 March 2017

This report proposes a new rule for inclusion in the Performance Based Standards scheme, adding a requirement for applicant vehicles to meet a minimum level of auxiliary braking performance. The purpose of the new rule is to ensure that PBS vehicles can maintain a safe speed on long, steep descents, without reliance on service brakes.

The principles and operational mechanisms of service brakes and auxiliary brakes are discussed as background information to the creation of the rule. Performance data on auxiliary brakes are used to calculate the theoretical capacity of such devices to aid in speed control during descents.

Example performance calculations are provided.

A separate section of the report examines the current PBS rule on directional stability under braking, and presents for consideration a number of changes to the deemed-to-comply aspect of that rule.

  • Summary
  • 1. Introduction
  • 2. Background
    • 2.1. The Braking Process
    • 2.2. Basic Brake Components and Operation
    • 2.3. Brake Fade
    • 2.4. Heavy Vehicles Descending Steep Grades
    • 2.5. Brake Standards and Regulations
      • 2.5.1. Australian Design Rule 35/05
      • 2.5.2. Australian Design Rule 38/04
      • 2.5.3. Australian Vehicle Standard Rules
      • 2.5.4. Australian Road Rules
      • 2.5.5. United Nations Economic Commission for Europe Regulation 13
  • 3. Auxiliary Braking Terminology
    • 3.1. Technical Support Group
    • 3.2. Types of Auxiliary Brakes
      • 3.2.1. Engine Brake
      • 3.2.2. Exhaust Brake
      • 3.2.3. Electromagnetic Retarders
      • 3.2.4. Hydraulic Retarders
    • 3.3. Controls and Integrated Systems
      • 3.3.1. Variations between Manufacturers
      • 3.3.2. Automatic Integration
      • 3.3.3. Cooling Considerations with Integrated Systems
    • 3.4. Australian Truck and Prime Mover Market
  • 4. Previous Austroads Research
  • 5. Auxiliary Brake Performance Data
    • 5.1. Auxiliary Brake Performance Calculations
    • 5.2. Auxiliary Brake Performance at High Vehicle Mass
    • 5.3. Auxiliary Braking on an Example Descent
    • 5.4. Practical Limits
  • 6. Design and Performance Standards
  • 7. Test Procedures
  • 8. PBS Rule Requirements
    • 8.1. Assessment by Calculation
      • 8.1.1. Step 1 – Calculation of Slope Force
      • 8.1.2. Step 2 – Calculation of Auxiliary Brake Force
      • 8.1.3. Example Vehicle Assessment
  • 9. Review of PBS Rule on Directional Stability Under Braking
    • 9.1. Background to the PBS Braking Standard
    • 9.2. Identification of Review Options
    • 9.3. Recommendations
  • 10. Conclusion
  • References
  • Appendix A Proposed PBS Auxiliary Brake Standard
  • Purpose and Intent
  • a) Purpose
  • b) Intent
  • Part (A) Restrain Speed
  • Definition
  • Measure
  • Test Specification
  • Part (B) Achieve Minimum Speed
  • Definition
  • Measure
  • Test Specification
  • Appendix B Fundamental Considerations
  • B.1 Auxiliary Brakes are Common on Heavy Vehicles in Australia
  • B.2 Range of Available Auxiliary Braking Equipment
  • B.3 Use of Service Brakes during Auxiliary Brake Tests
  • B.4 Safety of Testing
  • B.5 Certification of the Retardation Performance of an Auxiliary Brake
  • B.6 Use of Retrofitted Auxiliary Brakes
  • B.7 Calculation of the Downhill Speed Performance of a Vehicle Combination
  • B.8 Reliance of this Project on ECE Regulation 13 Status
  • B.9 Acceptance of Manufacturers’ Data or Declarations
  • B.10 Proving the Endurance of the Auxiliary Brake
  • B.11 Friction Limit Used in Calculations
  • B.12 Risks due to Excessive Retardation Being Applied on Unladen Vehicles
  • B.13 Auxiliary Brake User Interface Requirements
  • B.14 Classification of Individual Slopes
  • B.15 Minimum Speed Requirement
  • B.16 Initial Speed at the Commencement of a Descent