Here is a very pertinent illustration of the average speed
(acceleration-maximum speed) equation at work: a video of a Perth B series
accelerating to 130 km/h. The traffic on the adjacent motorway is maxing at
100 km/h. The film starts at Murdoch and ends just before Cockburn Central.
The distance between the two stations is 6.7 km, about the same as
Epping-Cherrybrook. The time between Murdoch and Cockburn Central is 3
mins, the time between Epping and Cherrybrook is 6 mins. No comment is
needed!

https://www.youtube.com/watch?v=8hGgVC_rOi4

For comparison, the closest equivalent run I can find on Sydney Trains
system is Heathcote-Waterfall which is 5.6 km and timetabled at 5 mins.

Tony P