Speed limits

International research suggests that motor vehicle speed is at the core of road safety, with higher speeds increasing the risk of crashes occurring as well as the severity of the consequences from the crashes that do occur (European Transport Safety Council September 2005, p1 and SWOV January 2007, p1).

In Australia, road authorities have historically set speed limits according to criteria that include road function, road alignment, prevailing traffic speeds and speed environment (covering roadside development as well as road and traffic characteristics).

A traditional focus on balancing safety and efficiency when setting speed limits is being challenged by a road safety perspective which states that safety should be the key deciding factor in setting speed limits.

Drivers react to many influences in choosing their speed and there is constant need to post realistic and credible speed limits to help achieve:
  • Voluntary compliance by the majority of motorists
  • Effective regulation of traffic flow
  • Reduced crashes
  • Optimal safety for vulnerable road users
  • Due regard for the amenity of people living along our streets and roads. 
International research into the tolerance limits of what the human body can survive when involved in a crash with or in modern vehicles (Tingvall and Lie 2008) supports speed limits being set lower in instances where the road environment does not provide adequate separation/protection from other road users, vehicles and roadside hazards.

It is RACQ’s preference that roads be upgraded to provide a more forgiving environment while maintaining mobility, rather than a blanket lowering of speed limits on existing substandard infrastructure.

However in high risk locations where road improvements are unable to occur in the short term, RACQ supports lowering of speed limits with appropriate changes in the traffic environment (including increased use of warning signs to highlight the change and the fact that the road is a high risk link) to assist in reducing crash likelihood and severity.  

A 10km/h speed limit reduction adds an additional four seconds of travel time to each kilometre, but using the section of Bruce Highway between Cooroy and Curra (which received this type of treatment in late 2008) as an example a sustained 11km/h reduction in 85th percentile speeds (Edgar and Tripathi 2011, p6) and a projected 16% reduction in crashes compared to the previous five years average was achieved (Edgar and Tripathi 2011, p7).

    1. Match speed limits to the function of road, its construction and environment in a uniform and consistent manner with adequate and appropriate signing.
    2. Retain current speed limit hierarchy in Queensland. This includes the default urban speed limit of 50km/h, with 40km/h or lower remaining as an option for road authorities in road environments that require them.
    3. Install on-road measures, e.g., line markings, to visually narrow a wide road in order to reduce speeds in areas where speed limits are valid but the physical road environment may conflict with general driver expectations.
    4. Upgrade sections of rural highway to reduce the number of speed limit changes due to substandard sections of road, e.g., re-align isolated rail crossings, widen and seal shoulders, replace narrow bridges, or rationalise the number of access points/intersections.
    5. Queensland Government to develop and maintain an Open Data database of active speed limit locations across Queensland, and for this data to be available to both the public and industries e.g., automotive and GPS manufacturers. 
    6. Queensland Government to perform speed limit reviews (preferably at least 50 per year) on their road network and publicise the results, including reviewing the number of speed limit changes along a length of road.
    7. Road Authorities to more readily apply guidelines for installation of ‘repeater’ speed limit signs – especially 300m after a change down in speed limit.
    8. Install electronic variable message signs to vary speed limits according to times or conditions where appropriate on major highly trafficked roads.
    9. Install speed activated warning signs to warn speeding drivers of their speed, remind road users of the correct speed limit and advise them of any hazards ahead.
    10. Take account of high pedestrian/cyclist activity as well as other vulnerable road users when setting lower speed limits and, where appropriate, support these with special engineering treatments, e.g., traffic calming.
    11. Ensure roadwork sites are adequately signed to protect road workers and road users and promote driver compliance with speed restrictions according to prevailing conditions, e.g., cover speed signs if lower limits do not apply when road workers or equipment are not present.
    12. Develop methods for making road work site plans publicly available online, to promote better compliance, auditing and enforcement.
    13. Consider radio break-in messages advising of works and speed limit at medium-long term road work sites, similar to what occurs in tunnel incidents/maintenance.
    14. Consider temporary speed limit reductions as an interim intervention on problem sections of road that can not be feasibly improved in the short term. 
  • Edgar, Neil and Tripathi, Santosh 2011, Queensland’s experience with speed limit reductions on ‘Black Links’, Safer Roads Unit, Department of Transport and Main Roads , Queensland, Accessed 23 May 2011:  http://casr.adelaide.edu.au/rsr/RSR2011/3BPaper%20078%20Tripathi.pdf

    European Transport Safety Council September 2005, ETSC Fact Sheet Number 06: Motor Vehicle Speed in the EU, European Transport Safety Council, Brussels, Belgium.

    SWOV Institute for Road Safety Research January 2007, SWOV Fact sheet: The relation between speed and crashes, SWOV, Leidschendam, The Netherlands.

    Tingvall, Claes and Lie, Anders 2008, "The role of Safe Infrastructure in Promoting Road Safety": Safe system approach, Swedish Road Administration, Online Presentation, Accessed 22 January 2008.

Things to note

The information in this article has been prepared for general information purposes only and is not intended as legal advice or specific advice to any particular person. Any advice contained in the document is general advice, not intended as legal advice or professional advice and does not take into account any person’s particular circumstances. Before acting on anything based on this advice you should consider its appropriateness to you, having regard to your objectives and needs.