Adelaide Hills Speed Limit Review

Phase 1 is a technical assessment of the sealed roads within the council area and includes a review of:

  • Crash History / Crash Rate
  • Function and role of the road
  • Road Geometry
  • Road Access Points
  • Verification of speed limit transition points
  • Verification of speed limit consistency

Crash History / Crash Rate
Crash history / crash rate is an important consideration as part of a speed limit review. The crash history is measured using what is known as individual risk (crash rate per 100 million vehicle kilometres) and ‘is the best way to provide a consistent relationship between speed limits and characteristics of the road and road environment, giving a hierarchy of limits that makes more sense to most road users.’ (Austroads 2008, Guide to Road Safety Part 3: Speed Limits and Speed Management)

The crash history was reviewed for the most recent 5 year period of each road section. An analysis of this crash data on the arterial road sections within the Adelaide Hills Council area identified that over the last five years (2009 – 2013) there were a total of 16 fatality crashes, 368 injury crashes and 631 reported property damage only crashes.

The map attached shows the risk of each of the arterial roads across the Adelaide Hills Council area.

Function and role of the road

Driver speed behaviour is influenced by the road user activity and visual clues associated with different road locations. Factors to be considered include the presence of pedestrian and cyclists, volume and type of traffic and traffic patterns or proximity to activities that may have an impact on travel flow and speed.

Road Geometry
Road geometric features also influence the speed at which motorists travel. Geometric features that were considered as part of this review include lane widths, shoulder widths, clear zone widths and horizontal curvature. Consideration was also made to the existing pavement marking of the roads.

Road Access Points
Road access points are any entry or exit point onto the carriageway, such as property accesses or intersecting roads.

For a property access to be included there had to be a visual clue to the driver that indicated vehicles may be joining the carriageway. The visual clue could be anything from buildings being visible, grand driveway entrances, distinctive signage to the property, etc.

Verification of speed limit transition points

Where speed limits change from one speed to another, the transition point should be near a visual clue which indicates to the change in road environment and a change in speed limit. As such, the department drove each road to assess the consistency of application of the transition points and identify any roads where transition points need to be amended.

Verification of speed limit consistency
In order for speed limits to be credible – the speed limit along a certain road needs to be consistent with other roads that “look and feel” the same. As such, the department drove each road to assess the consistency of application of speed limits across the Adelaide Hills Council area and identified any roads where speed limits did not appear to be applied consistently.

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