PD2/20 wrote:rubberman wrote:
Which is one of the reasons tram systems in Australia and round the world don't use centre islands. One reason amongst many.
My impression is that the tram extension from Victoria Square to the Entercentre was designed by people with a heavy rail background. Hence massive overhead (Which they call OCS, Overhead Catenary System, rather a dead giveaway imho), track that could take a locomotive, signalling that is prudent for trains with long braking distances, but irrelevant for trams, and centre platforms. The idea that others might share the road space with trams was fundamental to tramway development, but completely foreign to railway usage, except for oddities (shared rail ad road bridges in NZ I have seen

. Hence, centre islands.
The Adelaide tram system does not have catenary overhead in contrast to the contact/catenary wire configuration on the Seaford line. It is however tensioned which is an advantage in climates where there are significant temperature variations. The sleepered track from South Terrace to Brighton Rd uses conventional rail and sleepers made in Australia. Alternatives such as the grooved rail used in the street sections now has to be imported. What aspect of the signalling caters for long braking distances? When the level crossings were upgraded a few years ago, it was partly to alleviate problems with too short activation times. The alternatives to centre platforms are either kerbside running (which would be largely impracticable in King William St with its plethora of heavily used bus stops) or centre tracks with outside platforms (which then require fencing on the faces adjacent to the road lanes to protect passengers).
I apologise if my meaning was not clear. I was referring to the use of the acronym OCS as an example of the heavy rail mind set of present day Australian tram system designers. The dead giveaway being precisely for the reason you mentioned: most tram oriented designers would refer to it as simply "overhead", even more ancient types just say "trolley wire". Some people refer to OCS as Overhead Contact System too. However, because the wire still adopts a catenary shape, even though shallow, it is still correct too.
Well, as far as I know, there's no long braking distances, so why have the signals other than the crossing indicators ? That's my precise point. A permanent speed restriction at points, and drivers can see if it's safe to proceed. Or point indication at the outside. The former Victoria Square and Glenelg scissors termini and City depot junction had no signals and operated safely for decades. Why do identical usages now require signalling?
In King William St, if you had some of those buses running on the tramline as is commonly done overseas, you could eliminate the corresponding kerb bus stop, and use that extra room for standard tram stops. At the same time, taking those buses from King William St traffic lanes would help car, taxi and other bus users.