An integrated regular interval timetable (IRIT) is the same. With the same number of boats, a lot more can be achieved for passengers. Ridership goes up and net costs come down. It also allows space to be used more efficiently in a sometimes crowded maritime environment.
The essential elements of such a network are:
- all lines operate a strict clockface timetable. For example, departures from the local wharf, in the direction of the city, might always be 13 and 43 minutes past the hour. There may be additional departures in the peaks, but the underlying off peak pattern is retained through the peak period also.
- stopping patterns on inbound and outbound trips are symmetrical. This means inbound and outbound trips on the same line have the same duration.
- connections between lines are integrated at network nodes. Optimally, vessels arrive at nodes three or four minutes before the hour and half hour and then depart three or four minutes after the hour and half hour. This means passengers can transfer between lines without inconvenience.
That some passengers need to make transfers between lines to complete a journey may be seen as a disadvantage, but as transfers are timed, and the connection holds good for all departures, it is not a major inconvenience.
There are economic benefits in moving to an integrated regular interval timetable. This is because the significant jump in OD pair connections causes ridership to grow at a much faster rate than the operational costs.
The diagram below shows what an integrated regular interval timetable ferry network could look like in Sydney. Circular Quay is the hub for lines east of the city; Barangaroo is the hub for western lines. They are connected by the Darling Harbour line.
Features of the network are:
- new stops at Rhodes and Elizabeth Bay
- a new line for the Bays Precinct, with stops at Jacksons Landing, Rozelle and Glebe Point
- span of service for Watsons Bay extended to include AM and PM peaks (30 minute headways)
- timed transfers at Barangaroo and Circular Quay on the hour and half hour.
- Balmain East is a partial node, which means passengers on the Cockatoo Island Line can transfer here for departures to and from Circular Quay, or continue on to Barangaroo.
- timed transfers at Cockatoo Island, so passengers on the Cockatoo Island Line can connect conveniently with Parramatta River services.
Overall, convenient origin-destination pair connections increase more than fourfold, from 96 to 404.
One might expect that such an improvement in customer outcomes would be more costly, with additional vessels and increased taxpayer subsidy. No, it reduces net costs to taxpayers.
The following table compares the existing Sydney Ferry network with the integrated regular interval timetable network proposed in this post:
Current ferry operator payments and revenue sourced from Auditor General's Report Vol 7, November 2014
It is hard to predict the ridership impact of a fourfold increase in convenient OD pair connections - it is conservatively estimated here to be 40%. While there is an 12% increase in service hours, the extra costs in operator payments are more than offset by the extra revenue from ridership growth.
The peak fleet requirements are unchanged because of the efficiencies inherent in an IRIT network. Operating costs per service hour are also reduced as labour costs will be less.
The economic benefits don't end with reduced subsidies to the ferry operator. An IRIT network also means it is easier to share waterways with other users, such as cruise ships.
Sydneysiders are familiar with the impact of a large cruise ship berthing in Sydney Cove. It is disruptive for all vessel movements in the harbour.
If all lines in the ferry network are scheduled to arrive and depart Circular Quay around the hour and half hour, there are two 10 minute slots free every hour when no ferries are entering or departing Sydney Cove. This means a crowded maritime space can be safely shared for the economic benefit of Sydney.
For those who like details, the following table provides more information on what each line could look like in a Sydney ferry network based on IRIT principles.