When I talk to people about speed management, the conversation often ends up focusing on speed limits, especially the arguments for or against lowering the limit. Yet speed management is much more than changing the speed limit.
This is why a key theme we deliberately reinforce in the recently updated Austroads Guide to Road Safety Part 3: Safe Speed Management (AGRS Part 3) is that speed management is about much more than the number on the speed limit sign.
Speed is a major factor influencing both the likelihood of a crash occurring and the severity of the outcome when it does. Higher speeds reduce the time available to react, increase stopping distances, and most critically, increases the forces people experience when crashes occur. This is why, in the updated AGRS Part 3, we explicitly put speed at the centre of a safe transport system:
The updated AGRS Part 3 describes speed as the ‘regulating element’ of the Safe System. Road user behaviour, vehicle safety, road design and speed limits work together to determine whether crash forces remain within the limits the human body can tolerate. When these elements are optimally aligned, people are protected from death and serious injury.
This central role of speed is not a new concept. However, we deliberately strengthened its prominence throughout the updated AGRS Part 3 because it provides the foundation for understanding how Safe System interventions work together to manage crash impact forces.
One of the most significant additions to the updated AGRS Part 3 is the concept of a safe speed.
A safe speed is the travel speed that minimises the likelihood of death or serious injury while still enabling people and goods to move efficiently through the network. Different roads and streets have different safe speeds, depending on the road users that are present and the types of crashes that might occur in those environments. For example:
Lower safe speeds (e.g. ≤ 30 km/h) are desirable where collisions between motor vehicles and vulnerable users, such as people walking, cycling or using micromobility devices, are possible.
Moderate safe speeds (e.g. 50–70 km/h) are desirable where side or head-on collisions between vehicles are possible.
Higher safe speeds (e.g. ≥ 100 km/h) are feasible on roads where the potential for side and frontal impacts between vehicles is virtually eliminated, for example with the installation of side and median barriers.
While the term safe speed is new to the AGRS Part 3, the concept will be familiar to many jurisdictions, and is widely adopted internationally as best practice, for example in the World Bank and World Resource Institutes’ Guide for Safe Speeds: Managing Traffic Speeds to Save Lives and Improve Liveability. Across Australasia, terms such as safe and appropriate speed or target speed are often used to describe the same idea.
Ultimately, the term itself is not what matters. What matters is what it means in practice. If travel speeds are not already at the safe speed, what needs to change to achieve it? This question sits at the core of speed management.
Changing the speed limit is an obvious way to align travel speeds with safe speeds, but it is not the only solution. Safe speeds can also be achieved through safer infrastructure, safer vehicles, enforcement and vehicle technologies. Chapter 4 of AGRS Part 3 explores these broader interventions and highlights the importance of applying them in combination.
One example is the concept of engineering up. People often assume speed management means lowering the speed limit. However, engineering up takes the opposite approach. Instead of lowering the speed limit, the road is upgraded so higher speeds can be accommodated safely. This might include treatments such as median barriers, roadside barriers, intersection upgrades and separated facilities for people walking and cycling. This approach is often adopted on strategic roads where the efficient movement of traffic is a priority, although the investment and space required mean it is not practical in every situation.
The engineering up approach demonstrates that speed management is not inherently about making roads slower, it’s about matching speeds to the level of protection provided. The same principle also applies to vehicle safety technologies. Features such as Intelligent Speed Assistance, Automated Emergency Braking and connected vehicle technologies are becoming increasingly important tools for reducing both crash risk and crash severity.
Enforcement is another tool that is often overlooked in discussions about speed management. However, it works best when used to support, rather than replace, safe speed limits and safe road designs. AGRS Part 3 now includes extensive guidance on developing speed enforcement programs and understanding their impact on travel speeds and crashes.
While speed management extends well beyond speed limits, speed limits remain an important part of the speed management approach. Sections 5 and 6 of the AGRS Part 3 focus on speed limit setting frameworks and the implementation of safe speed limits. This is guided by 4 principles:
Minimise harm – speed limits should support safe speeds that reduce the likelihood of death and serious injury, recognising the limits of human tolerance to crash forces.
Align to movement and place – speed limits should reflect both the movement function of roads and the needs of the communities and places they serve.
Support community wellbeing – safe speeds should contribute to broader outcomes, including accessibility, amenity, public health and transport choice.
Effective change management – changing speed limits to align with safe speeds requires significant changes in perception and behaviour among decision makers, practitioners and the public. Successful implementation requires time, support and resources.
Together, these principles move speed limit setting beyond traditional approaches that focused primarily on traffic movement or existing operating speeds.
The change management principle is particularly important because, no matter what approach is taken, creating a transport system where most travel occurs at safe speeds cannot happen overnight. Achieving this vision will require a combination of infrastructure upgrades, policy changes, community engagement and staged speed limit changes over many years.
The AGRS Part 3 recognises that Network Safety Plans will play an important role in this transition. They provide a practical way to identify where speed limit changes, infrastructure upgrades, or a combination of both are needed across a network. Network Safety Plans can also be used to develop speed limit change programs that progressively reduce exposure to death and serious injury risk, supporting the ultimate goal of zero deaths and serious injuries by 2050.
The most important message we want people to take from the updated AGRS Part 3 is that speed management is much more than just speed limits. Safe speeds are at the heart of a Safe System and can only be achieved when speed limits, road design, infrastructure, vehicle safety and enforcement working together.