It is a rail, bus or ferry timetable that operates at a fixed time interval all day - say every 30 minutes. An integrated regular interval timetable goes a step further by also ensuring passengers have a short wait time at hubs before transferring to another service or mode.
A network wide regular interval timetable was first introduced on the Netherlands rail network in 1932, but it was the Swiss Federal Railways who took it to a new level of sophistication. This happened from 1982 with the first iteration of Taktfahrplan, which loosely translates in English to "pulse timetable".
The simplified network diagram below illustrates how it works in practice:
|A 30 minute regular interval timetable with connecting nodes|
The Red Line train departs Station F shortly afterwards, providing convenient connections for transferring passengers from both the Blue Line trains.
Any crossover point in the network (in this example, they occur at 15 and 45 minutes past the hour), creates opportunities for similar symmetrical transfers to other modes, such as the bus line shown connecting at Station C.
What is unique about the Swiss approach is the importance of Taktfahrplan as a strategic driver of transport planning - convenient timetables with timed transfers at network nodes underpin the entire public transport network. They are devised 20 years in advance of implementation and help set priorities for infrastructure upgrades. Technology is not the driver, but a means to achieve a purpose, which is to improve the performance of the timetable.
Regular interval timetables are ideally suited to urban transit ferry systems. They make ferry travel easier for customers and simplify operations, leading to lower subsidies by taxpayers. But with the notable exception of Brisbane Ferries, the concept has not been embraced in Australia. Perhaps it's because the benefits are not well understood.
Benefit 1 - a better customer experience through simplicity and connections
Benefit 1 is really two benefits, but they are closely related. Simiplicity comes from the regularity of the timetable - the service always departs from a stop at the same minute interval every hour, so it is easy to remember the timetable. But because it is also a pulse timetable, timed connections at interchanges are also regular and consistent.
The following example shows how easy it would be to navigate across the Sydney ferry network, if it was based on these principles.
Let's imagine you live at Elizabeth Bay and a ferry now stops at Elizabeth Bay twice an hour. The ferry departs for the downtown terminal at Circular Quay 15 minutes before and 15 minutes after the hour, every hour. In the outbound direction - towards Double Bay - it departs 12 minutes before and 18 minutes past the hour.
Within 15 minutes you could be at Circular Quay or any other stop on the Double Bay line.
As all ferries arrive at Circular Quay a few minutes before the hour and depart a few minutes after the hour, you would be able to transfer at the Quay to the Manly Ferry or any Inner Harbour ferry with just a short waiting time. This means that within a further 15 minutes, seven more destinations can be reached.
And in another ten minutes - 40 minutes since the journey started at Elizabeth Bay - a total of 17 destinations could be reached by ferry. This does not include numerous other destinations through transfers to other modes at Circular Quay, Milsons Point, McMahons Point etc.
So you can see that from two very simple principles - regular intervals and timed connections at interchange points - a ferry network can be easy to comprehend for the passenger and provide access to multiple destinations with great convenience.
This is the first in a six part series on regular interval timetabling: Parts 2 to 6 will follow in coming weeks.