Safe System design

The design of places where pedestrians are present should align with Safe System principles. In general, safe system aligned measures for pedestrians either:

• separate pedestrians from motor vehicles and other high-speed traffic (including cyclists), or
• ensure impact speeds in the case of a collision are no greater than 30km/h.

Further information on the importance of the above points is discussed below.

Safe System-aligned measures for pedestrians and cyclists require either full separation of pedestrians and cyclists from vehicles or, where this cannot practically be achieved, low-risk travel speeds, typically not exceeding 30km/h. This assessment method is based on the extent to which design and operational combinations meet the following three key criteria:

• injury severity
• crash likelihood
• exposure to potential conflict. 

Full separation, by definition, eliminates the likelihood of crashes, while travel speeds not exceeding 30km/h help to ensure impacts at legal speeds have a low risk of death or severe injury to vulnerable road users. Travel speeds not above 30 km/h are vital to achieving the lowest practical risk levels for several reasons:

• In a highly complex traffic setting, drivers and riders may reach the threshold of their information processing capabilities if travelling at high speed. At 30km/h or less, decisions can be made in a much more timely fashion.
• Driver willingness to give way increases with reductions in travel speed. Thus the frequency of conflict between motorists, and pedestrians and cyclists, can be reduced further at lower travel speeds compared with legal speeds commonly encountered today.
• Vehicle stopping distances are substantially reduced with lower travel speeds.
• Past research on pedestrian safety shows that in about half of all pedestrian fatalities, no braking occurred and therefore the travel speed is too often the impact speed. This is likely to be true for cyclists as well.
• The research on the biomechanical tolerance of humans to various vehicle impact speeds shows a rapid rise in the risk of a pedestrian (or cyclist) fatality above an impact speed of around 30km/h. For serious injury risk, the corresponding threshold impact speed is likely to be much lower. Risk is even more acute when the striking vehicle is a tram/LRV or other large vehicle and/or when children and older people are involved.[1]

The Austroads research[2] identified pedestrian facilities that are Safe System aligned (known as Primary Safe System interventions), and those that are not fully aligned with Safe System principles but can support or make incremental improvements to safety and/or mobility for pedestrians (known as Supporting Safe System interventions). The alignment of these measures for different movement and place street families is also provided in the research.

The safe system approach in relation to people walking is discussed further in:

PNG: A Safe System for walking