Metro said that the single track section of the Altona Loop creates a bottleneck as it only allows a single train to travel in one direction at one time so a train has to wait for the opposite-running train to clear before it can enter the Loop. This forms Metro's argument for turning the Altona loop into a shuttle service so that any delay within the Loop will not be passed on to other subsequent stations along the Werribee line.
The most obvious, permanent solution is to duplicate the Altona Loop. However, this takes time. Somebody has suggested an interim measure to overcome this limitation of the Altona Loop.
During the morning peak as well as the day interpeak period, most Altona passengers will be travelling to the City. Run the Werribee train through the Altona Loop to Flinders Street just in this direction. These are indicated by the dark-blue arrows in the map shown above. As there is no opposite-running train through the Altona Loop, it is possible to double the train frequency from the current 1 train every 20 min to 1 train every 10 min. This will be considered a true increase in the number of services that benefit not just Altona but the whole of the Werribee Line.
Altona passengers getting to Werribee have two options, either taking the City-bound Train to Newport to take a Werribee-bound Express Train or take a shuttle bus to Laverton Station to catch a Werribee-bound Train. Passengers from Newport, Spotswood, Yarraville, Seddon or Footscray getting to Altona can take the Werribee-bound Express Train, alight at Laverton, then take the City-bound Train through the Altona Loop. The Werribee Express Train will help to reduce the impact to these passengers.
During the evening peak and at night, most Altona passengers will be getting home from the City. So now reverse the train direction through the Altona Loop, that is, running towards Werribee. These are indicated by the red arrows in the map shown above.
Under this model, trains will be running unidirectionally through the Altona Loop at all times except during weekends and the bottleneck problem will be solved. Most importantly, the train frequency can be greatly increased. If the Altona Loop Shuttle Train is running, this shuttle train may still cross path with the Werribee Express Train at the connecting stations, for example, at Newport, as it needs to turn around. This will probably still require one train to wait for the other. With the suggested model, this problem will be eliminated.
This is not a perfect model as it will still bring inconvenience to some passengers. But it is one that merits serious considerations from Metro and the Transport Department, as I think it is viable and will bring about real service improvements.