Please find a link to NSW Transport to enable all residents to have their say about reducing the current speed limit or leaving it as is.

https://www.saferroadsnsw.com.au/HaveYourSay.aspx

A resident has kindly calculated the time difference; the road section in Question is 3.12 km long.
Time taken at various speeds are:
80km/hr = 2min 22 sec
70km/hr = 2min 42 sec
60km/hr = 3min  9 sec
50km/hr = 3min 47 sec