An overall framework for safe and credible speeds requires a stronger functional approach to management of the road network.

Reductions in travel speeds save lives and injuries, and these benefits have been clearly demonstrated on South Australian roads. The 2003 reduction in urban speed limits to 50km/h produced a reduction of over 20% in urban crashes. Other targeted speed limit reductions, such as in parts of the Adelaide Hills where the speed limit was reduced to 80km/h and selected 110km/h rural roads with a lower limit of 100km/h, have produced similar results.

Reductions in average travel speed across the network is the most effective, swift way to reduce road trauma and would produce significant and immediate road safety benefits. A reduction of 5km/h in average travel speed would reduce rural casualty crashes by about 30%, and urban casualty crashes by about 25%. A blanket application of the default speed limit on rural roads (excluding national highways) would be projected to save over 20 fatalities and serious injuries combined each year.

Travel speeds have consequences for crash risk, and also for injury severity when a crash occurs. Biomechanical research into the capacity of the human body to absorb crash energy without significant harm suggests that safe travel speeds would ideally be less than 30km/h in areas where conflict with people walking and cycling is possible, less than 50km/h where side impacts are possible, and less than 70km/h on roads where head on collisions are possible (see figure 5). This illustrates the need to address speed within a functional approach to road management.

Reductions in speed and speed limits can also be the most publicly contentious way to reduce road trauma. Sustained improvement in speed management will only occur with the support of the community and other stakeholders, and the adoption of a total change management approach. It will be vital for all stakeholders to understand, and be able to explain, the importance of speed management to a safe system, along with the community gains that can be achieved from even small reductions in travelling speed.

The safety benefits of small speed reductions are not always intuitively obvious and more public information will be provided to address the community’s overestimation of related costs and underestimation of related benefits. For example, while up to 5 minutes is added to a 100km trip when travelling at 100km/h, rather than 110km/h, travelling at 100km/h uses on average 8% less fuel than travelling at 110km/h.

The wider benefits of reducing speeds, including better fuel consumption, lower greenhouse gas emissions, less traffic noise, and better support for active travel modes, contribute to South Australia’s environmental, sustainability, and wellbeing objectives.
 

Appropriate Speed Limits

International work has shown that to achieve our vision, speed limits need to be set and enforced taking into account potential crashes and the likely outcomes of these crashes given the physical impact on the human body.
The default speed limit in South Australia is 50km/h in urban areas and 100km/h in rural areas. Speed enforcement and speed limit reductions will be targeted to roads above the default limit with high crash rates or risk, and where land use and infrastructure planning does not justify a limit above the default. 

Projects for retrofitting safe and credible speed limits will be progressed in rural and metropolitan areas, taking into account:

• sustainability and liveability aims of the 30 Year Plan for Greater Adelaide, and the need to support safe movement for pedestrians and cyclists
• the concentration of trauma in rural areas close to Adelaide, including fringe areas undergoing changes in traffic volumes and demographics
• increased understanding of the impact of a rural road network of two-way two lane roads with speed limits of 110km/h, which is out of step with countries with the best road safety record.

Figure 5 Collision - force and risk of fatality

Research into the capacity of the human body to absorb crash energy indicates that speeds would ideally be less than 30km/h in where conflict with people walking and cycling is possible, less than 50km/h where vehicle side-impacts are possible and less than 70km/h where head on collisions are possible.

Speed is a critical factor in every serious crash, and speeding was identified as a contributing factor in an estimated 36% of fatal crashes for the 2009-2011 period.

Compliance with Speed Limits

Whatever the speed limit, improved compliance with, and enforcement of, the limit plays a vital role in improving the safety of all road users. The current network of fixed safety cameras in urban areas will expand and include mid-block and pedestrian crossing cameras. These automated enforcement approaches will continue to be supplemented by targeted deployment of SAPOL personnel operating a range of technologies including mobile cameras and mobile radars at their disposal, and targeting roads with high crash risk.

New technologies have the potential to increase the range and effectiveness of enforcement resources. Average speed cameras that measure the speeds of all vehicles between relatively distant points on the road can be more effective and fairer than one-point speed cameras. They can monitor all vehicles over a long section of road continuously as they do not penalise momentary breaches of the speed limit. Focusing on major regional and interstate routes, the development of a comprehensive point-to-point speed enforcement system will initially focus on the key routes into and out of Adelaide.

The penalties in place to deter users who may otherwise flout the law and create unacceptable risk to others are a critical part of the mix of speed compliance interventions. The current range of penalties for speeding offences does not match the fundamental safety risk associated with the offence, whether for lower or higher end offending. Changes will be made so that the penalties for higher level speeding more closely correlates with the road safety risk.

Over the life of this strategy, it is expected that new vehicle technologies, such as intelligent speed adaptation will begin to provide the ultimate support for the vast bulk of drivers who have no intention of breaking the law, but may inadvertently travel above the speed limit. Speed limiting devices could also be targeted to recidivist offenders.

*Free speed with 4 second headway