The last time this was half tried it failed for some reasons,
what i suggest is one way traffic on John st Rose inn st and High st,
with two way traffic on Parliament st and Bateman quay.
This allows for a small loop in the center using Bateman quay and an outer loop using Irish town Dean st and the new bridge,
traffic on Vicar st should only turn on to the bridge.
install a roundabout at the parade,with big on street level pedestrian crossings set back from the roundabout this will help reduce traffic speed which i believe should be set at 20km to discourage thru traffic this will be safer for walkers, cyclists and drivers and is a sort of share the space idea which will lead to a cleaner,nicer retail experience in the city center