The Glen Waverly line, is being removed from the City Loop, so as to free up capacity for more services on other lines such as Lilydale and Belgrave.
This clogs up Flinders Street, and somewhat limits the capacity of that station.
At the same time, the Craigiburn line is gaining in popularity, especially as more fo the outer area is being developed into housing estates.
By extending the Glen Waverly line trains to Essondon, shall help boost capacity in/along the inner Melbourne section of the Craigiburn line.
This project shall provide, three areas of major benefit to the existing and future customers, as well as to the train system itself.
In peak hour, you could run some services all the way to Craigiburn.
Selected trips on the Alamein line can also be extended to Essondon.