The above last two photo's are called 'motor vehicle restriction points' that reduce the pathway width to 1.4 metres at the midpoint of the rails on a 2.4 metre shared path, though I would say that are also cyclist restriction points.
These are quite dangerous for cyclist and I note that Bicycle Queensland recently had stated that these type of barriers are dangerous and had asked the Queensland Road and Transport department to have them removed. But as road traffic engineers who no nothing about adequate cycling infrastructure they obligingly refused.
In the Netherlands motor vehicle barriers look like this......
They are also used to slow mopeds down while riding on the cycle paths. No chance of impaling yourself anywhere here. Infrastructure that is designed to be respectful of cyclists and not to enforce barriers to cycling.