Courtesy of the Busways website. (used without permission)
Trials are currently undergoing in western Sydney of double decker buses. Double decker buses have been in Sydney before but the last time that they were in active service by the then State Transit Authority was in 1986.
At the moment they will be confined to the T-Way running between Parramatta and Liverpool but I fear that that may be as far as they are ever allowed to roam.
The problem that double decker buses face is not low slung power lines or even low bridges trees but low branches of trees. Unlike power lines or bridges, trees do not care about building regulations; also unlike power lines or bridges, the responsibility to look after them lies not with electricity companies or NSW Transport but with local councils.
There are 42 local government authorities across Sydney. If you've ever sat in any room of more than 42 people, you'll very soon realise that there is the potential for a host of different opinions (remember the old adage that if you have ten people in a room, then you have twenty opinions). If you then take representatives from organisations instead of just the people themselves, then getting them to agree on anything is like trying to herd cats. Herding cats is a task which in theory can be achieved though.
Local government would object most strongly to having to wear the costs of trimming trees because the expense comes with zero reward for them. The City Of Sydney demonstrated this earlier this year when the decision to stagger bus stops in Clarence St in the city resulted in the loss of parking meters. Although the council should be responsible for installing signs and street furniture, they argued successfully that because they had suffered the loss of even a relatively small revenue stream, that NSW Transport should bear the cost.
If this applies to just one street in one local government area, then what hope is there of 42 of them agreeing to wear the costs of continuous tree trimming just so NSW Transport can run buses?
Double decker buses would improve traffic flow immensely throughout Sydney because with greater capacity per bus, it allows the running of fewer buses or alternatively if the fares are lowered to make bus patronage more attractive, would take more cars off the road. Although this sounds like simple common sense, you have to remember that common sense isn't common and especially when you have self-interested parties with different desires in conflict with each other.
No council in their collective right mind is going to commit to a program of increased costs unless there is a system of compensation in place. No state government is going to commit to a program of compensating local government if the logistics of such a plan are as immense as they have the potential to be and especially in an environment of massive scaling back of expenses.
The main reason why Sydney will not put double decker buses throughout the city is that it is an expense/logistics nightmare. The people who would benefit from it most (ie commuters) are not seen as people to be responsible to but as mugginses from whom revenues can be extracted, and for that reason primarily we're more likely to see another toll motorway than double deck buses in Sydney.
Place bets now. A motorway finished first or double decker buses in the city?
Addenda: as I was writing this, Infrastructure NSW has announced an "underground bus terminal" at Wynyard. This is without a doubt the cheapest solution as the tunnels have already been built.
What it does mean though, is that they'll never jam double deck buses a) down the tunnel and b) down George St.
... Odds have shortened on the motorway being built.