#26 Protected Roundabouts

As described previously in Post #15, roundabouts are a primary safe system treatment to minimise the likelihood and severity of intersection crashes while regulating traffic flow. For vulnerable road users, however, some roundabouts may increase the actual or perceived risk relative to other intersection treatments[1]. Subsequently, in lower speed zones protected roundabouts are a relatively new approach including specific design features to improve the safety of pedestrians and cyclists. These features include traffic calming measures to reduce entry and approach speeds, and dedicated paths to separate motorised traffic from pedestrians and cyclists. In some cases, partial or full signalisation (i.e., applied to one or more approaches) may also be appropriate where higher traffic volumes and/or specific modes require prioritisation.

[1] Austroads Guide to Road Design Part 4B: Roundabouts

Example of a protected roundabout in Victoria, designed by Road Solutions.

Raised Safety Platforms

Raised safety platforms on approaches to roundabouts can incorporate zebra (wombat) crossings to provide safe pedestrian crossing points set back from the roundabout itself. The set-back distance needs to be balanced against the desired speed reduction and the risk of queues forming within the roundabout. Vertical deflection of the platform serves to reduce vehicle speeds, with the amount of speed reduction dependent on platform dimensions (height, length and ramp gradient). Platforms also potentially increase the visibility of pedestrians by raising their profile and may be vertically aligned with connecting paths for easier transition onto the crossing. Platforms may be coloured (including with traditional ‘zebra’ stripes) to attract the attention of motorists and potentially match connecting pathways.

Mode Separation

Where roundabout entry and circulating speeds cannot be contained to 30km/h or less, it is appropriate to separate cyclists from motorised traffic. Cyclists may thus be directed to pedestrian crossing facilities, but in some cases, a separate cycle lane may continue through the roundabout on the outside of the general traffic lane/s. While, ideally, cyclists and pedestrians should each have separate dedicated and continuous pathways, this may not always be feasible within the available road space and resource constraints. In some cases, shared pedestrian/cyclist paths may be suitable.

Considerations

Many factors need to be considered in the design of protected roundabouts. The Austroads Guide to Road Design Part 4B (Roundabouts) and Part 7 (New and Emerging Treatments) provide detailed information on options and variations. The concept of protected roundabouts is relatively new in Australia, and positive case studies are many and varied internationally.