Cycle paths around the outside of a roundabout may provide a suitable alternative for people who do not wish to cycle in the roundabout. Off-road path alternatives at roundabouts will generally be shared paths, ie pedestrian volumes and needs should be included when determining path width and alignment.
This section includes:
Where an off-road path network is provided, it should not be assumed that cyclists will (or should) use these, unless cycling is specifically prohibited on the roadway. Off-road path networks may seem too indirect to some cyclists. Thus all roundabouts should also be designed with on-road cyclists in mind.
The bi-directional nature of off-road paths can result in safety implications for cyclists crossing roundabout approaches and departures as motorists may not expect cyclists coming from the “wrong” direction (i.e. cycling anti-clockwise around an off-road path network). Therefore it is preferable that off-road paths are one-way only for cyclists and circulate in the same direction as the circulating traffic. It is also particularly important to reduce speeds of motor vehicles entering and exiting the roundabout where cyclists may be crossing the legs. Also, sufficient intervisibility between path users and motorists should be ensured at crossings on roundabout departure legs.
The suitability of an off-road path network to provide for cyclists depends on the gaps available in traffic. If flows are too heavy, cyclists will not be able to find a gap to cross the approach and departure lanes. To determine the suitability of a crossing point for cyclists, the Austroads ‘Pedestrian Facility Selection Tool’ can be used, with some adaptations to account for cyclists. The tool will yield a level of service rating for specific crossing provisions which will help in determining the suitability of path crossings at roundabouts.
The design criteria for pedestrian platforms presented in the New Zealand Pedestrian planning and design guide are appropriate for crossings shared by pedestrians and cyclists on path networks at roundabouts; note that this includes the criteria that the speed limit is 50 km/h or less, and that the crossing platforms should be preceded by a feature that causes vehicles to slow. For the exit the roundabout provides this. For the approach, an extended splitter island, narrowed lane, and the close proximity of the roundabout would meet this requirement. Design information is also available in the Traffic Control Devices Manual Part 6.
Because platforms at roundabouts are separated by islands, uni-directional designs are feasible with departure ramps more gentle than approach ramps.
For a 'small' roundabout the crossing is usually located 6m from the circulating lane. For compact roundabouts, the platform and an associated zebra crossing permit the setback to be further. The crossings should be set back at least 6 m but no greater than 20 m from the circulating lanes. A set back of 6 m allows one vehicle to queue without blocking the crossing or intruding into the circulating lanes, and 12 m permits two vehicles to do so. Research has shown that further than 20 m from the limit line vehicle speeds are too high to allow for pedestrians and cyclists to cross safely (Campbell et al., 2012). The Austroads Guide to Road Design Part 4B recommends a distance of 12 m (2 car-lengths) across both approach and exit.
If it is deemed appropriate to provide an off-road path network at a roundabout but crossing one or more approaches and departures is difficult and high risk, grade separated crossings should be considered. For path design refer to Austroads Guide to Road Design part 6; Paths.