With the opening of the 2 extra lanes on the Harbour Bridge (replacing the tram tracks in 1959) and the opening of the Cahill Expressway across Circular Quay there was an ever increasing amount of traffic making its own way across the harbour, to and from North Sydney. At this time, all the traffic was squeezed onto the 6-8 lane Pacific Hwy through the middle of North Sydney. a major problem was the high demand for right turn movements, especially into the 4-lane Miller St, with a large percentage of traffic heading towards Cremorne/Mosman via Military Rd, Cammeray/Northbridge via Miller St and into Chatswood/Roseville via Willoughby Rd. The Warringah Freeway was mooted as the answer to these traffic problems. While the first stage would not remove through traffic from the pacific Hwy, it would allow traffic to bypass North Sydney and distribute it to the major Northern Beaches routes. Coupled with the prposed Gore Hill Freeway, through traffic to Lane Cove, Hornsby and points along the Pacific Hwy would eventually be able to bypass North Sydney.

The Department of Main Roads had never been able to fully sustain its program of maintainence, reconstruction and moderate new construction, and new sources of revenue were required to finance major new construction projects. Consequently, the Sydney Harbour Bridge (Administration) Act, 1932 was amended in 1960 to enable the Department to use surplus toll revenue for the property acquisition costs of the Warringah Expressway, among other projects, from Ernest St to Bradfield Hwy. Further legislative action was taken to extend the provisions of the Sydney Harbour Bridge (Administration) Act, 1932 by the passing of the Sydney Harbour Bridge (Administration) Amendment Act, 1962. This Act allowed Harbour Bridge toll surpluses to cover the costs of property acquisition costs between Ernest St & Miller St, Cammeray and the cost of construction between Bradfield Hwy and Miller St. While approval had been given to utilise surplus toll revenue from the Sydney Harbour Bridge Account for the acquisition of land for, and the construction of, freeways as approaches to the Sydney Harbour Bridge, it was recognised that the available funds would be insufficient to complete these works and that a further source of funds was required. These funds for the Warringah were raised by a 33% increase in motor vehicle taxation rates in 1962.

When serious planning and design was started, the corridor had already been gazetted but what lay in the way of the DMR bulldozers was 1km of densley packed residences along Arthur and Alfred Streets. All of it went, the bulldozers cutting a swathe through North Sydney before reaching the open parkland near Ridge St. Construction began in late 1965, with heavy earthworks required to pass beneath Falcon, Ernest and Miller Streets.

At this time, freeway construction was relatively new in NSW and Australia, the Warringah Freeway being easily the most ambitious project undertaken, which it needed to be. Included in the project were some different construction techniques, allowing the Freeway to utilise its maximum potential. Firstly, the entire first stage was constructed with four carriageways in a 3-2-2-3 mainline lane configuration. On/off rmaps and their associated slip lanes were constructed where required. The middle two carriageways were unique in that they were reversible, allowing traffic to travel in either direction depending on the time of day, and including massive sign gantries capable of of changing the sign messages according to the direction in which the carriageway was operating. Movable medians and well-placed on/off ramps allowed a N-S-S-S operation in the morning peak, a N-N-N-S set-up in the afternoon peak and a N-N-S-S setup in offpeak times. For each carriageway, an asphalt surface was used for the travelling lanes and a concrete surface used for the shoulders, creating a high level of delineation. Two bus bays were also constructed between Falcon and Ernest Streets (near the Cremorne Depot) allowing for 'Express'/'via Freeway' buses to change drivers.

At the north end, Miller St, a temporary connection was provided to Chandos St until the anticipated extension to Willoughby Rd was completed. Construction of the first stage from Bradfield Hwy, North Sydney to Miller St, Cammeray was opened to traffic in June 1968.

The Department of Main Roads prepared a promotional film to commemorate this very significant project. Two short excerpts from this film have been uploaded by the National Film & Sound Archive here and here. I highly recommend clip 2 for the fantastic signage shots.