When it was announced in
November 2014 that Sydney was getting six new Inner Harbour ferries,
expectations were raised that they would be "some of the fastest on Sydney
Harbour", operating on Inner Harbour routes from Watsons Bay to Cockatoo
Island.
Unfortunately,
fast ferries don't always work well in urban transit systems.
As
observed astutely by Kamen and Barry (2006):
"Wheels
on steel rails or smooth concrete ... produce negligible resistance compared to
the frictional and wavemaking effects of a hull in water. And land vehicles
enjoy essentially 100% propulsive efficiency between driveline and useful
thrust. Public land vehicles also benefit from an economy of scale: A
single operator can drive a train that moves well over a thousand commuters, or
a bendy bus or multi-car streetcar holding a hundred or more passengers."
Frictional
resistance of a vessel hull in water is significant. As Kamen and Barry noted, "propulsion power is
roughly proportional to speed cubed, and most costs are therefore also
proportionate to speed cubed or at least squared."
This
is why Sydney Ferries' SuperCats, operating at speeds of up to 26 knots to Rose
Bay and Watsons Bay, need to be refuelled daily. The more sedate First
Fleeters, with a maximum speed of 12 knots, only refuel once a week.
Fuel
and maintenance costs are not the only issues. Australian Maritime Safety
Authority (AMSA) standards are more demanding for a ferry operator when a
vessel's propulsion power exceeds 750 kW. Vessels in this category must
be driven by a Marine Engineer Driver (MED) Grade 1. Most Sydney Ferry masters
are not qualified at this level.
For
this reason, I'm guessing that the new Inner Harbour ferries, due to enter
service later in 2016, will have a propulsion power of 749 kW. They will then
only require an MED 2 at the controls, but reach a modest speed of 20 knots at
full throttle. That will be about the limit, given the superstructure and passenger
capacity proposed for the new vessels.
There's
nothing wrong with 20 knots for most of the Inner Harbour. The geography of
Sydney means a slow ferry to Cremorne Point, Kurraba Point or Balmain East
competes quite effectively with land transport.
The
real problem lies with Watsons Bay and Rose Bay. Even with improvements in
passenger loading, the new vessels will not be able to keep the current Eastern
Suburbs timetable if their maximum speed is 20 knots.
Why
not change the timetable then?
Timetables
are constrained by mathematics as much as propulsion systems. It takes about 11
minutes for a SuperCat travelling at up to 26 knots in open water to make the
6.2 km journey from Rose Bay to Circular Quay. After adding time for passenger
loading and unloading, the round trip can be completed in 30 minutes. That's
tight, but one SuperCat can operate a 30 minute interval service to Rose Bay.
With two SuperCats, it could be a 15 minute interval.
If
the current Watsons Bay wharf was upgraded to a better design, a round trip to
WB, with a stop at Rose Bay in both directions, could be completed in 60
minutes with a speed of 26 knots in open water. This would require two vessels
with a 30 minute interval.
This
neat scenario falls apart if a slower, 20 knot vessel was to replace the
SuperCats. The 11 minutes from Rose Bay to Circular Quay goes up to 13 minutes.
Rose Bay round trip goes from 30 to 34 minutes; Watsons Bay round trip goes
from 60 to 68 minutes. Result misery.
The
20 knot vessel option does not work for the Eastern Suburbs because, with
clockface 30 minute headways, the slower speed will lead to long layovers at
either end and an extra vessel added to the runnings: a very wasteful outcome
all round.
So
what's to be done about the Eastern Suburbs? My guess is that the SuperCats
will continue operating on Eastern Suburbs runs for some time - and the new
Inner Harbour ferries will probably not venture to either Rose Bay or Watsons
Bay.
What
this means for Sydney's ferry fleet strategy is unclear. The First Fleet
Ferries have plenty of life left in them. With nine First Fleeters and six new
Inner Harbour boats to come into service over the next 18 months, there is
capacity to expand the Inner Harbour network. This comes at a cost, of course.
With the new Inner Harbour ferries, plus the recently announced four new
Parramatta River ferries, the complexity of Sydney's diverse ferry fleet could
be greater than ever.
Ferry
passengers of Sydney must wait with baited breath to see what transpires.
Reference:
Kamen,
P. & Barry, C. (2006). Urban Passenger-Only Ferry Systems: Issues,
Opportunities and Technologies. In R. Delpizzo (Ed.), Sustainability in the Maritime
Industry: A Collection of Relevant Papers. New York: Society of Naval
Architects and Marine Engineers.
