I enjoy my 8km cycle commute to work and occasionally try beating my best time for the commute. But speed often gets me, and others, into trouble. The bikeway is a fantastic way to get to work but it can get a bit crowded. Since I cycle in from the south east most of the route has cyclists and pedestrians sharing the path. In some of these cyclists travelling at speed are a major hazard - to themselves, pedestrians and other cyclists. Sections like the Goodwill Bridge, Victoria Bridge, Southbank and the old Bicentennial Bikeway have so many cyclists, walkers and runners that things can get a little hair raising during peak commute times.
I sympathise with the idea of a pro-cycling Perth political to implement speed limits for cyclists as reported in this article. The problem is, they are not really practical. Cyclists are not legally required to have speedometers fitted so there is no way they can know whether they are travelling over the speed limit. I have not checked the road rules but I suspect that it would be impossible to fine a cyclist for speeding. It is more likely that they would be fined for reckless or dangerous cycling.
Speed only really is an issue where there is potential for conflict between pathway users travelling at different speeds. The risk of conflict is increased as the space per user decreases, and the speed differential of users increases. Which is why the guidelines recommend that pathway width increase on busy shared pathways, or users are provided with separated pathways where conflicts are high.
There may be a need for guidelines to recognise that the speed differential of cyclists is also a risk. Busy rural roads have passing lanes to allow fast cars to bypass caravans and slow trucks. For cyclists the equivalent would either be a wider cycleway (as recommended in the Cycling Super Highways) or providing both on-road and off-road options. The former may be preferable but the latter may be the pragmatic answer that is implementable.
A 3m wide shared path and 1.5m wide bike lanes is often far more palatable for roads engineers than a 6m wide shared pathway. But effectively cyclists have the same amount of space allocated to them. And by separating the shared pathway and cycle lanes there is potential that confident cyclists with a need for speed will choose the bike lanes while the slower cyclists and pedestrians share the pathway.
This is all conjecture as I have not seen any research on this. But something worth considering when deciding on the appropriate solution for a corridor.