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Thursday, 26 February 2015

A well designed transit network is a safe network

Sydney Ferries has an excellent safety record. In the last eight years, with over 110 million passenger journeys, there have been no fatalities related to Sydney Ferry operations.

It would be wrong, though, to be complacent. Congestion on Sydney Harbour and the risks posed by passenger crowding on poorly designed wharves mean that a tragedy may not be far away.

An often neglected cause of safety risk is poor network design and timetabling. Timetables which are not periodic - where there is inconsistency in stopping patterns or departure times through the day - make it difficult for crews to develop safe muscle memory. As a vessel leaves Circular Quay for Mosman, for example, the movements of other vessels around them may be different depending on the time of day, so potential risks may not always be anticipated.

On its return to Circular Quay, the Mosman ferry may berth at Wharf 4 (east or west) or maybe somewhere else if the crew are about to take a crib break. This inconsistency simply adds to complexity at our main ferry hub.      

A ferry system is not a closed system. Other vessels using Sydney Harbour are impacted by ferry operations and they also are put at greater risk by the lack of a regular pattern in ferry movements.

A recently introduced "solution" to the problem at Circular Quay is a decision by Roads and Maritime Services (RMS) to fine ferry masters $500 for breaches of the code of conduct for navigation in Sydney Cove. A breach may include proceeding south of the knuckle at the northern edge of the Passenger Terminal before a berth has become available at Circular Quay. The problem with this solution is that, in some instances, the timetable does not schedule a sufficient buffer between departing and arriving vessels. This means passengers are inconvenienced by being forced to sit in motionless vessels at the Sydney Cove waiting line.

A more sensible approach would be to implement integrated regular interval timetables. In my proposal:
  • all western lines, including Cockatoo Island/Woolwich, will hub at Barangaroo to free up berths at Circular Quay.
  • all ferries on eastern lines, plus the Darling Harbour line, arrive at Circular Quay between 2-7 minutes before the hour and half hour; all depart Circular Quay 2-7 minutes after the hour and half hour.     
This means there is a minimum separation of four minutes between arriving and departing vessels from the Quay.

It also creates two 15 minute windows every hour when there are no ferry movements at Circular Quay, enabling other vessels, including cruise ships, to operate without interfering (or being interfered by) ferry movements.

This 30 minute periodic timetable would operate all day, but could be supplemented in peak periods on some lines if justified by demand (eg an extra Rose Bay service could run to create 15 minute headways in the peaks only) without disturbances to the underlying structure.

In a timetable designed this way, vessel movements become very predictable. What happens in one period also happens in all periods. The mitigation of a systemic risk in one period will also mitigate that risk in all periods.

Not only that, RMS would not have to fine ferry masters $500 for observing the timetable.      




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