1988: Pymble Interchange opens

The original proposal for the Pymble Interchange. Full Citation below.

The Pymble Interchange is the intersection of the Pacific Highway with Mona Vale and Ryde Roads at Pymble. Mona Vale Road and Ryde Road intersect beneath a short road tunnel that carries the Pacific Highway above. It was completed in 1988. 

Prior to 1988, it was a typical intersection, but by the early 1970's it had created traffic problems for North Shore motorists.

The intersection of the Pacific Highway, Ryde Road and Mona Vale Road in 1973. Full Citiation below.

In 1973, the NSW Government proposed a three-level interchange. The first level would carry traffic for Mona Vale Road and Ryde Road. The second level would serve as on- and off-ramps for traffic approaching or exiting the Pacific Highway, and the Pacific Highway would be raised to form the third level. Under the scheme, through traffic on the Pacific Highway would be signal-free as they cross the intersection. 

The rail bridge crossing Mona Vale Road, which carries the North Shore Railway line, had to be realigned and shifted eastwards to accommodate the interchange. 

Source: Anonymous. 1973. "Plans for first 3-level interchange in Sydney". The Sydney Morning Herald, January 4: 3. 

The interchange was not completed until 1988. It was opened to traffic on December 21 1988. 

Source: Silverman, N. 1988. "$21m present for motorists". The Daily Mirror, December 20: 7. 

The same article also described an earlier scheme in which an overpass would carry through traffic on the Pacific Highway, as in the original 1973 scheme, but traffic signals would be placed to manage traffic entering or exiting the Pacific Highway at the same level as Mona Vale Road and Ryde Road. I've enlarged it for your viewing.