VicRoads Cycle Notes 21 (August 2013) has advice on the widths of off-road shared use paths. It is not the most recent. Austroads Guide to Road Design Part 6A: Paths for Walking and Cycling (AGRD06A) and the Netherlands CROW publication are more recent. Still, it is worth noting that even back in 2013 VicRoads were aware of what we in Canberra need and still do not have.
Shared paths are ripe for conflicts. As the traffic increases, so do the conflicts between pedestrians and cyclists. There comes a point where a small increase in traffic results in much greater confusion and the traffic on the path slows. We could call this congestion, however, in this case it is people and bikes. The carrying capacity of the shared path increases with width, however, shared paths are inefficient due to lack of conventions. The problem is systemic. The same path width can carry much more traffic if the pedestrians and cyclists are separated without taking up more space on the verge. The reason is simple: cyclists are much faster than pedestrians, and the speed differences create friction (comparative speeds are 25km/h for bikes and 5km/h for pedestrians).
VicRoads comes to the conclusion that a 4m wide shared path provides WORSE outcomes for ALL path users than two separated paths that total to the same width, in this case a 2.5m wide cycle only path and 1.5 m wide pedestrians only path.1
The ACT Government should listen. Shared paths are not the best option for Principal Cycle Routes (CBR Cycle Routes). The same space and material carries greater capacity when the paths are separated. No doubt the paths are safer too. Principal Cycle Routes should be cycle only paths and separated from pedestrians.
Principal Community Route (PCR) –A subset of Main Community Routes (MCR) that form direct links between town centres. There are routes that are to include route labels and branding.Active Travel Facilities Design – Municipal Infrastructure Standards 05 (MIS05) (ACT Government, April 2019)
VicRoads looks at the nature of the interactions between pedestrians and cyclists.
The number of delayed passing increase significantly as the volume of pedestrians increase due to the speed differential between cyclists and pedestrians.Passing and meetings, VicRoads Cycle Notes 21, Widths of Off-Road Shared Use Paths, August 2013
While it is accepted that we drive on the left in Australia, pedestrians do not generally think it applies to shared paths. Cyclist will ride left as they do not want to collide with another cyclist coming at speed around a corner. Pedestrians seem completely unaware of this. As the path gets wider, pedestrians seem to scatter themselves randomly across the surface (Lake Burley Griffin share path) leaving the cyclist little choice but to swerve around them, instruct them to stay left or ring a bell, so they get clear. Such difficulties are avoided with separated paths for cyclist and pedestrians, should everybody remain in their own area.
The surface of the path is important too, as pedestrians and cyclists have different preferences. It is not just aesthetic. Bikes have wheels (with usually no suspension) and we have feet. Small undulations between pavers are unnoticeable to pedestrians but create vibrations through the bike at speed. Vibrations increase fatigue, can blur vision, slow the bike down, and increase the cycling effort. This is why cyclist favour smooths surfaces such as asphalt. Asphalt paths need to be made well and protect from moisture and tree roots or they will become rapidly cracked and uneven.
1 VicRoads Cycle Notes 21, Widths of Off-Road Shared Use Paths, August 2013.