Humps are ugly, and a real pain if you drive a Volkswagen!
Nor are they needed. St George for example works quite well. About 90% of cars respect the 30 kph limit, or close to it.
You got to be joking??
I have yet to see a street with speed bumps removing traffic to the point, I see drivers not slowing down for those bumps and flyover them.
One way streets encourage through-traffic. Just look at Adelaide. They become arterial roads.
John Street is not intended to be closed to cars permanently, but the plan allows for that during certain events.
Speed bumps are inconveniences. People who want to use it as a fast way of getting from north to south would find a different street to use because the speed bumps would slow down their BMWs and Jaguars enough that it would be too much of an inconvenience.