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The problem

Rising traffic volumes have put strain on several low-risk residential intersections around Dunedin, as well as on many which were already a priority for upgrades. Limited visibility and acute approach angles posed further safety issues at some of these intersections. Dunedin City Council (DCC) therefore wanted to improve the safety and efficiency of these intersections, but the capital cost of installing standard permanent upgrades across all of them would be cost-prohibitive. In order to improve multiple intersections, upgrades therefore needed to be light and low-cost.

How the project responded

DCC installed trial roundabouts at 11 unsignalised intersections to test roundabout sizes and layouts. As well as enabling a smaller layout than usually designed for permanent changes, the trial format meant small changes on-site could easily be carried out. The changes included:

  • ‘new road layout’ signage
  • painted central islands and road markings
  • narrower traffic lanes
  • speed humps on the central islands at half of the intersections only
  • ‘slip lanes’ for people on bikes at the Musselburgh intersection only.

The changes were intended to improve safety by:

  • slowing vehicles
  • reducing pedestrian crossing lengths
  • encouraging cyclists to take the lane (or use the dedicated slip lanes at Musselburgh).

By making initial changes as a trial, the changes were likely to be better received by the public, as they can be adjusted or removed if they prove not to be functioning well. Following the initial roll-out, changes included adding speed humps to the central islands of those originally without, and installing reflective flexible bollards along the intersection medians and edges.

Adjusted trial roundabout layout

Adjusted trial roundabout layout. Credit: Dunedin City Council.

Adjusted trial roundabout layout

Adjusted trial roundabout layout. Credit: Dunedin City Council.

What was learned

Before and after video data collection is ongoing and will be used to monitor road user behaviour at the trial sites. DCC received a lot of feedback, both negative and positive:

  • most people understand why the trials are being done
  • key stakeholders and bus operators are in favour of the roundabouts
  • drivers are often surprised by the new intersection layouts appearing suddenly
  • social media responses show initial negative sentiment is decreasing while approval or acceptance of the changes is rising.

Lessons learned include that:

  • ‘new road layout’ signage is insufficient to alert drivers to the new layouts; additional traffic management measures would be beneficial for the first few days
  • speed humps on the central islands substantially increased the visibility of the new central islands in darkness and when it was wet
  • reflective flexible bollards to mark the new painted medians and intersection edges further increased the visibility of the new layout
  • design sector consultants need reassurance around the development of non-standard traffic control device designs.