Most ferry passengers probably don't care much about efficiency. Inefficiency is usually not visible and nor are the consequences.
But the efficient use of assets and resources, especially labour, makes a big difference to the cost of running a ferry system and impacts on the economics of new routes or service frequency on existing ones. That's why everyone should be very concerned about operational efficiency.
From the operator's perspective, a key efficiency measure is the ratio between crew roster hours and ferry service hours. It is desirable in each roster line to increase the time crews spend driving vessels on timetabled services and reduce time in non revenue earning activities. Some non revenue earning hours are essential, including mandatory crib (meal) breaks, positioning trips and training and safety drills, but minimising "sitting around" time can make significant savings for the operator and the taxpayers who subsidise the operator.
So how does a timetable impact on efficiency?
If a timetable follows an irregular pattern, and vessels can return to a hub at any time, long periods of down time in excess of mandatory crib breaks are almost inevitable. It is unlikely that the period between finishing a run before a crib break or restarting after the break will correspond exactly to the mandatory time allowed for breaks.
By contrast, a regular interval timetable is modular. In a 30 minute interval network, vessels return to a hub a few minutes before the hour and half hour and depart a few minutes after the hour and half hour. This means crib breaks can always occur in neat 30 or 60 minute blocks with minimal wastage.
This level of modularity is only possible in a regular interval timetable.
Further efficiency improvement can be made by stopping the practice of resting vessels when the crew take a crib break. If crews returning from a crib break are assigned to whatever vessel needs crewing, then vessels would achieve higher utilisation rates and reduce requirements for berthing capacity at busy terminals like Circular Quay.
The upside for passengers is that all of these efficiency gains would make expansion of the ferry network more attractive to Government. And that means a better customer experience.