Install pedestrian underpasses at all King William St intersections from North Tce to Flinders/Franklin Street.
These could include access to the tram stops and, of course, provide appropriate facilities for disabled/elderly pedestrians. This would improve pedestrian and vehicular traffic flows along the spine of the CBD, where both forms of traffic are at high levels.
Better still, create a pedestrian mall underneath King William St, complete with travellators to facilitate pedestrian movement between the city's zones: cultural, retail and commercial.
This mall could be lined with shops, as is the case with some pedestrian tunnels in cities overseas. This would actually encourage people to walk more around the city as they would experience fewer delays - pedestrians could move from North Tce to the Central Market in 5 minutes.