The A3 is a major metropolitan arterial route in Sydney. It was formerly designated as Metroad 3. The A3 runs from its intersection with the A8 at Mona Vale at the north end, to the southerly of its two intersections with A1, the Princes Highway, at Blakehurst the south end. The highest speed limit on the is on Mona Vale Road. It is a major connector between most of the major radial routes emanating from central Sydney, and a major link between the northern and southern parts of the Sydney tolled orbital freeway. It is the most direct, although not necessarily the quickest, route across Sydney between the South Coast and the North Coast. Most of the route has been progressively upgraded to three lanes in each direction. Sections which are only two lanes in each direction remain, between Beverley Hills and South Hurstville, along Homebush Bay Drive, and between St Ives and Terry Hills. Between Mona Vale and Terry Hills, most of the eastern section of Mona Vale Road is only 1 lane in each direction. Much of the route becomes very congested in peak hour. The name "A3" is the route allocation for the route as a whole, not a road name. The A3 route runs along a whole series of differently named roads. From north to south they are:
What is now called A3 was initially designated to become a major north-south metropolitan arterial route in 1964, when the route incorporating several existing local arterial roads was designated as 'Ring Road 3'. It was subsequently re-designated 'State Route 33' between 1974 and 1993, and then re-designated 'Metroad 3' after April 1993. It is the only one of Sydney's 'Metroad' routes that has not changed alignment since the Metroad system was adopted in 1993, although there were changes to the route prior to that. In August 2013, as part of the alphanumeric route scheme, Metroad 3 was decommissioned and was designated A3. After 1964, upgrading projects were commenced, with the construction of new De Burghs Bridges over the Lane Cove River between Pymble and Ryde, and the duplication of Ryde Bridge over the Parramatta River between Ryde and Rhodes. Many projects have been undertaken over the ensuing decades to widen most of the route in stages to three lanes each way, although no proper freeway sections have ever been constructed. Grade-separated crossings have been constructed where A3 crosses other major roads: at the Pacific Highway at Pymble, M2 Hills Motorway at Macquarie Park, Epping Road at North Ryde, at Victoria Road at Top Ryde, at the intersection with Australia Avenue and Underwood Road, at Homebush, at the M4 Western Motorway and Parramatta Road, at Flemington, the Hume Highway at Chullora, and the M5 South Western Motorway at Beverly Hills. A major deviation of part of the route was built, relocating the arterial route to the west between Rhodes and Wiley Park, to bypass the Strathfield bottleneck and improve access to the Olympic Precinct at Homebush Bay. The deviated route includes Homebush Bay Drive, Centenary Drive, and an upgraded Roberts Road though Chullora and Greenacre, connecting to King Georges Road near Wiley Park. The road upgrades, new bridges and connections for this deviation were completed in stages between 1983 and 1998. This replaced the original route along Concord Road, Coronation Parade, and Punchbowl Road, which passed through a very congested section at Strathfield and was also problematical to widen. The original route was subsequently given the route allocation State Route 27 which was decommissioned in 2004.
