I have received information from someone who travels regularly on this road. They have informed me that the 60 km/h zone begins just after crossing the Greenhill Primary School, near Hand Ln (-31.05951918521311, 152.80391343907073), and continues until it changes to a 100 km/h zone after crossing Walsh Lane (-31.0515035472532, 152.78151452194655). I have verified this information using NSW Speed Data and Google Street Maps, and have hence updated it.