2.4 Safe Mobility
To comply with the Safe System and to achieve a safe road environment, road agencies need to move towards maximising safe mobility.
While road safety has always been a focus for road agencies, safety has in the past been typically addressed through reactively addressing road network locations with a crash history. As outlined in Austroads (2016a), road safety practitioners are moving towards the Safe System approach which incorporates a more proactive approach to road safety based on the assessed potential crash risk of the road. Key features of the Safe System approach and how it addresses various issues associated with crashes are outlined in Table 2.3.
|Issue||Safe System approach|
|Understanding of critical speeds at which fatal and serious injury (FSI) crashes occur for different crash types||Biomechanical tolerances are core to the vision of eliminating FSI crashes.|
|Road user error||A forgiving road and roadside is core to the Safe System. FSI crashes should not occur because of driver error. Vehicle and infrastructure improvements should be used to reduce impact forces (should a crash occur) to below human tolerances, and therefore reduce crash severity.|
|Shared responsibility||Road managers/designers share the responsibility for safe travel outcomes by accommodating road user error.|
|Design requirements||It is paramount that new infrastructure assists in eliminating death and serious injury. This also includes speed management and separation of road users travelling in different directions or of different mass.|
|Crash severities addressed||FSI crashes should be the main aim and starting point in site identification. Minor and non‑injury crashes may be useful to provide additional information, but are not the core focus.|
Source: Austroads (2016a).
While the Safe System approach has been adopted in Australia and New Zealand for over ten years, it is evident that there is a lack of clarity on how to integrate the approach into the daily activities of engineering practitioners. Austroads has commissioned a project titled Translating Safe System Research and Knowledge into Practice: A Guide for Practitioners to provide guidance on this (Reference to be added once published).
Harm minimisation is an integral component of Safe Systems. That is, road design and traffic management needs to also consider how to reduce the severity of crashes when they occur. In engineering terms, harm minimisation means the consideration of impact energy: as manipulating speed, mass and crash angles can reduce crash injury severity. Speed is at the heart of a Safe System and aspirational design speeds include: 30 km/h (car vs pedestrian/cyclist), 50 km/h (car vs car side impact at 90 degrees) and 70 km/h (car vs car head-on). Self‑explaining roads and the principles of Movement and Place in urban design provide effective ways to support differing speed environments and road functions. Some common ways to minimise harm for different road environments include:
- altering the impact angle away from 90° and lowering the impact speed at intersections
- protecting corridors with flexible barriers to prevent high speed lane departures on rural roads
- lowering the speed or separating vulnerable road users from other motorised vehicular traffic.
The shift towards the Safe System approach and delivery of safe mobility is a key component of network operation planning. As outlined in the Guide to Traffic Management Part 4: Network Management (Austroads 2016b), a network operation plan (NOP) which is the output of the network operation planning process, aims to guide the operation and development of road/transport networks towards managing competing priorities.
An NOP underpins higher level strategic plans and should be developed in full consultation with stakeholders and the community. One of the key planning principles in an NOP is to provide safer road travel for all road users and move towards the broader application of the Safe System.
The Guide to Traffic Management Part 4: Network Management (Austroads 2016b) provides a level of service (LOS) framework that allows users to assess the various LOS measures for five road user types (private motorists, transit users, pedestrians, cyclists and freight operators) and the five needs (mobility, safety, access, information and amenity). The LOS framework enables practitioners to measure LOS gaps because of implementing road strategies. This enables practitioners to implement an NOP as the LOS framework helps to understand the LOS for various road users and their needs. As safety is one need, safety LOS defines the various safety needs for various road users and provides a measure to assess how effectively the road environment meets these safety needs.
Accessibility-based NOP extends the traditional NOP by focusing on targeted road users and their journeys rather than on just links. The accessibility-based network operation planning LOS framework, incorporates safety as a user need and is based on Safe System principles (as outlined in Austroads (2015d)). By expanding to include various road users and their needs, the framework assists practitioners in understanding the appropriate safety LOS for the various users relative to the intended function and role of the road. The role may change by location, day and time along a road. For example, while a road may be classified as an arterial or highway, it may go through an activity centre and therefore its function may change. This may result in local area traffic management facilities being put in place to improve safety, mobility, amenity and access to the activity centre for vulnerable road users. The concept of accessibility-based NOP is shown in Figure 2.2.
Source: Austroads (2016b).
From a hierarchical sense, the Guide to Traffic Management Part 4: Network Management (Austroads 2016b) is above the Guide to Traffic Management Part 5: Road Management (Austroads 2017e). Further still an NOP is above any individual road management plan and guides how a road should be managed to meet the objectives of the NOP.
Practitioners should refer to an NOP to implement safe mobility. Doing so enables the clarification of the function and role of different segments of the road at different segments of time. Additionally, it enables practitioners to understand the safety LOS for the various users of that segment of road, for that time. An example of safe mobility as opposed to a more traditional approach, balancing efficiency with safety, is the shift towards the use of fully controlled right‑turns as opposed to filter right-turns, where safety may pose a risk. While the filtered right‑turn may offer some efficiency gains, by allowing right-turns to filter through the opposing through movement, in some cases it may pose a safety risk. Therefore, fully controlled right-turns are preferred from a safe mobility perspective. The Guide to Traffic Management Part 5 (Austroads 2017e) and the Guide to Traffic Management Part 6 (Austroads 2017f) provide guidance to practitioners on the management of roads from the mid-block and intersection perspective respectively. To comply with the Safe System, practitioners should focus on implementing strategies that maximise safe mobility.
Austroads (2015e) outlines that speed management is a core component of a Safe System and remains the best opportunity for rapidly reducing road trauma. The critical role of speed in the Safe System was recognised by the National Road Safety Strategy with safe speeds being a key pillar of the Safe System. Physical devices may be used to achieve a speed environment that is compatible with the road activity and often requires alteration of the road geometry to reduce the speed of the environment. Practitioners should consider speed management as a potentially effective approach to managing safety risk. Speed management is discussed throughout the Guide to Traffic Management, the Guide to Traffic Management Part 5 (Austroads 2017e), the Guide to Traffic Management Part 7 (Austroads 2015b) and the Guide to Traffic Management Part 8 (Austroads 2016c).