Major work has begun to untangle tracks at the junction where the Cranbourne and Pakenham lines merge in Melbourne.
Speed restrictions at the section of rail line cause trains to slow down as they move towards the junction, in Dandenong.
Once works on the Cranbourne Line are completed in 2023, the new parallel tracks will increase reliability making it easier for trains to run to the timetable.
The upgrades will allow trains to run six time and hour on the Cranbourne Line.
The Level Crossing Removal Project aims to make the Cranbourne line completely free of level crossings by 2025.
The line will be fully duplicated by 2023 as crews will build eight kilometres of new track and duplicate two rail bridges along the route.