William Street's northern end is at Walcott Street in. It travels southwest along one block, for, before turning southwards. After it reaches Vincent Street, and the southern edge of Mount Lawley. The road continues in a south-south-westerly direction, at the eastern edge of Hyde Park and the western edge of. One block beyond the park, within the suburb of, William Street intersects Bulwer Street, which connects to three parallel arterial roads – Lord StreetBeaufort Street, and Fitzgerald Street – as well as the major north-south road, Charles Street. William Street realigns itself one block further east through a reverse curve. At this point, it intersects Brisbane Street, which bring southbound State Route 51 traffic to William Street. Prior to the restoration of two-way traffic on Beaufort Street, all southbound traffic was redirected via Brisbane Street to William Street. Beyond this intersection, the road is the southbound component of State Route 51. It continues in a straight line for to Roe Street, and is at the eastern edge of from Newcastle Street to that point. The Horseshoe Bridge takes the road over the Fremantle and Joondalup railway lines, passing between the Perth railway station and Wellington Street bus station. Beyond the bridge, the road continues in its south-south-westerly direction through the Perth CBD. It intersects all the major east-west routes. At the southern end of the bridge is Wellingtion Street. This is followed by Murray and Hay streets, which are pedestrian malls to the east; and then St Georges Terrace, which is a through-route for vehicular traffic. One more block takes it to an intersection with Mounts Bay Road, to the west, and the Esplanade to east. After one more block, alongside the Elizabeth Quay Bus Station and railway station, the road ends at Riverside Drive. This intersection also connects a Mitchell Freeway exit ramp and Kwinana Freeway southbound entrance ramp, components of the Narrows Interchange.
Public transport
William Street is serviced by buses running through Northbridge. Most of these services deviate via Elizabeth QuayBus Station before continuing to their destination.
William Street began as a two-way street, and during the era of trams in Perth, there were tram lines along it. In the late 20th century and early 21st century, William Street was two-way north of Brisbane Street, and one-way southbound on the other side. In 2008, the section between The Esplanade and Wellington Street returned to two-way traffic. Further conversion occurred in 2010, when the Horseshoe Bridge was changed back to two-way traffic, and in 2013 the section between the bridge and Newcastle Street was converted.