Bus 596 loops to the Hornsby Station. Hornsby station is great as it offers two alternate routes to the city: North Shore and Northern line. Northern line is an express which takes about 37mins or so and the North Shore line takes a bit longer. We love the area and commuting to the city is pretty good hence been living here over two decades now..
There is an express bus, but I get the train. You can get the fast Newcastle or Gosford express from Hornsby Station that gets you to the city in 40 minutes, or a slightly longer journey across the harbor bridge on the north shore line. Hornsby is great because it is serviced by two train lines (Northern and North Shore), so if there is a problem on one, then use the other. From Hornsby Heights to the station I ride my bicycle. It takes 20 minutes and I park right at the station making use of the bike lockers. That way I save time AND get my daily exercise.