@kuldalai why those lines and not the Bendigo/Ballarat/Geelong lines?
It has always been a mystery as to why loco hauled trains gave trouble between Traralgon and Sale, whereas the same loco hauled trains running between Geelong and Warrnambool did not . Same sort of rural verging on coastal atmosphere .
It would also appear that where a track has mixed passenger and freight tarffic, problems are unlikely to occur whereas lines with passenger traffic only some instances occur, and lines with disc braked DMU only seem to give the most problems .
With the DMU and lx . Remember that with the RFR upgrades IIRC the level crossings are track circuited on Geelong and Ballarat, but axle counters on Bendigo and Traralgon because of differenet contractors .
Also the more cars you have in a consist the higher area of wheel the contact with the rails.
So with axle counters now on Stony Point Metro allow single Sprinter operation, whereas VLP on all their lines single Sprinter operation is not allowed, albeit originally it was . (Min VLP Sprinter consist allowed now is 2 cars.)