Use of Auxiliary Brakes in Heavy Vehicles

Austroads Freight Taskforce (2014-2015)

Tiger Spider has been engaged by the Austroads Freight Taskforce to conduct a review into the use of auxiliary brakes (Engine brakes / retarders) on heavy vehicles down steep descents. The project will incorporate data collection from stakeholder surveys in conjunction with vehicle testing and simulation studies in order to better understand the issues and develop strategies to encourage the safer operation of auxiliary brakes on very long steep descents and reduce noise in residential areas.

Use of Auxiliary Brakes in Heavy Vehicles

Austroads Freight Taskforce (2014-2015)

Tiger Spider has been engaged by the Austroads Freight Taskforce to conduct a review into the use of auxiliary brakes (Engine brakes / retarders) on heavy vehicles down steep descents. The project will incorporate data collection from stakeholder surveys in conjunction with vehicle testing and simulation studies in order to better understand the issues and develop strategies to encourage the safer operation of auxiliary brakes on very long steep descents and reduce noise in residential areas.

by admin

The Objective

The purpose of this research was to review the current use of auxiliary brakes operating on very long and steep descents and recommend safe, appropriate and adequate measures to improve road safety and amenity.

Road safety objectives include:

  • Developing a better understanding of driver awareness and behaviour in regard to the correct use of auxiliary brakes
  • Development of an operator check-list that will encourage safer driving on steep downhill grades through the correct use of auxiliary brakes
  • Determining what the maximum speed limit(s) should be for heavy vehicles on steep downhill grades if a differential speed limit were used instead of a low gear sign.

The Process.

Australian road authorities commissioned this research into the correct use of auxiliary brakes on heavy vehicles in response to a number of serious incidents involving runaway trucks on very long, steep grades and continued noise complaints from the community. Their objectives were related to both safety and amenity and included:

  • Developing a better understanding of driver awareness and behaviour in regard to the correct use of auxiliary brakes
  • Development of an operator checklist to encourage safer driving on steep downhill grades through the correct use of auxiliary brakes
  • Determining what the maximum speed limit(s) should be for heavy vehicles on steep downhill grades if a differential speed limit were used instead of a low gear sign
  • Developing a better understanding of the current strategies and approaches for auxiliary brake use in residential areas
  • Developing an understanding of the attitudes of heavy vehicle drivers and local councils to auxiliary brake use in residential areas and driving strategies used to reduce the impact of noisy engine brakes.

The research included a substantial literature review of previous studies related to auxiliary brake systems, crash statistics, brake noise, vehicle standards, brake system maintenance and future technologies. Surveys of truck drivers and local governments were also undertaken and a field testing and simulation program was designed and run to assess differential speed limits on long steep grades.

The Results

  • A driver training framework has been proposed which includes elements of safe, efficient and polite driving.
  • Recommendation has been proposed that measures to address noisy engine brake issues, in particular noise cameras and sound barriers should be targeted at areas where community concern is the greatest.
  • Recommendation has been proposed that Australian regulators need to consider mandatory auxiliary brake system performance requirements for certain categories of heavy vehicles.
  • Recommendation has been proposed that Performance requirements may need to be incorporated into both the Australian Design Rules (ADRs) and the Performance Based Standards (PBS) Scheme.
  • A framework for assessing differential speed limits based on end of slope brake temperatures and computer simulation has been developed.
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