National steer axle mass limits

This report examines issues associated with potential changes to mass limits for steer axles on heavy vehicles in Australia. The project aimed to establish optimum steer axle mass limits, with a particular focus on suitability for road trains, to accommodate the needs of the transport industry into the future. The practical engineering issues associated with a heavier load on the steer axle and the fitments of wider tyres were investigated via industry consultation. A pavement life cycle costing analysis was undertaken to determine the pavement maintenance costs associated with increased steer axle limits. The load wear cost model selected for this task was embodied in the Freight Axle Mass Limits Investigation Tool (FAMLIT) which was used to quantify the marginal differences in pavement deterioration. A selection of 25 road segments was used for analysis with 30 loading scenarios. The study found that the optimum steer axle mass limit is 7.0 t, with a wider (greater than 375 mm) tyre size. This increase in steer axle limit can be applied to road train operators with minimal change in operations. The finding suggests that it is possible to increase the steer axle mass above 7.0 t before an increase in cost is realised, however an increase to 7.0 t allows a margin of safety for the limitations of the testing (variations in tyre construction and inflation pressure) on which the reference loads are based. An increase to 7.0 t will also be consistent with current limits in the Northern Territory.


  • English

Media Info

  • Pagination: 83p

Subject/Index Terms

Filing Info

  • Accession Number: 01594939
  • Record Type: Publication
  • Source Agency: ARRB
  • ISBN: 9781925294941
  • Report/Paper Numbers: AP-R505-16
  • Files: ITRD, ATRI
  • Created Date: Mar 30 2016 10:49AM