The Dandenong line is one of the most heavily patronised in the suburban network. With the recent increases in patronage its capacity has been severely stretched and various proposals have been put up as potential solutions.

The goals for the project are (in order of priority):

1. A significant increase in capacity. Smart Passengers predicts that the increase in patronage will continue due to the high cost of petrol and growing environmental awareness. Therefore a minor stop-gap solution (eg a timetable alteration to allow a small number of extra trains to run) is not acceptable except in conjunction with a major improvement.
2. Reliability and punctuality. These are controlled by operational flexibility - the ability of the infrastructure to cope with a situation not planned for in the timetable. Usually this means more infrastructure - extra stabling sidings, extra crossovers or passing loops, or more tracks.
3. Allowance for more express runs. Smart Passengers research indicates that overall journey time is one of the most sigificant factors passengers take into consideration when evaluating transport options; travel time from the Casey/Cardinia area on a stopping-all-stations train is much slower than a car trip on the freeway. Shoulder-peak and off-peak express services will also help spread the peak-hour load.
4. Grade separation. Delays to bus services which cross the Dandenong line are already high; the addition of a large number of extra services will bring traffic to a standstill. Cost-effective grade separation can be achieved by lowering the level of the railway and building underground stations with bus bays on top - see also Policy on grade separations.

In order to satisfy all of these criteria, the option which stands out is full quadruplication (see Policy on track amplifications). It provides more capacity than triplication or a two-tier service using the third platform at Oakleigh; it keeps express and stopping trains separate for better punctuality; it allows for all-day express services.

There is no requirement for every station to have four platforms. Express services should only stop at major stations (eg Oakleigh, Springvale, Dandenong) and the rest of the stations could be laid out like West Footscray in order to save space and money. Casual observation indicates that very little land acquisition would be required, and only a few station car park spaces lost, if this method was adopted.

The junction at Caulfield will be a significant barrier to increased services. To realise the full potential of four tracks a flyover would be required, in order to keep fast and slow trains separate.

The ideal time to start construction of a fourth track will be just after the Monash Freeway capacity project is completed in late 2010. That way when train services are interrupted express bus services can use the freeway to carry passengers to the city. A delay of a few years will see the additional capacity on the freeway taken up by normal growth, resulting in delays to the replacement bus services. Major works should be scheduled for weekends and public holidays, as was done for the Middleborough Road grade separation.