Re: TRAMWAY "SAFEWORKING"

["Ron BEST" <ronbest@bigpond.com>]

Use of what, in railway terms, is called "automatic single line track block
(ATB)" was very common on tramways. E.g., Melbourne - last application was
on "The hump" or "Mt Buggery", i.e. Miller St private-right-of-way (PRW)
near the workshops (I believe there were some spectacular failures of that
particular installation, most/all due to driver error). Also, Ballarat
(still there on the tourist tramway), Bendigo, Geelong, Brisbane etc.

Junctions were sometimes controlled by colour-light (or, earlier, semaphore)
signals, worked from a signal box. Sydney had 27 signal boxes, on elevated
supports above the footpath (one is at the tramway museum at Loftus).
Melbourne had a few (most facing points are now "automatic", the driver
setting the route via "power on/power off" or via a transponder). I don't
know if Melbourne still has any. They used a signal that looked like a
smaller version of a railway three-light signal head - green for proceed on
the "main line", white for proceed on the "branch" and red for "stop". The
"main line" wasn't always the "straight" route e.g. at Franklin St (top of
Swanston St), when the points were set for the "turnout", i.e. the through
line north along Swanston St, the "green" was shown. This location also had
a numerical display (initially, in the form of two side-by-side
traffic-signal type heads, later a seven-segment mechanical unit) to
indicate to drivers of terminating trams, where to stop and shunt.  (BTW,
similar displays are now used at depots to indicate, I think, which road
each arriving car is to be stored on.) A set of standard traffic signals is
used to control the junction in PRW at St Kilda Jn between St Kilda Rd and
Queensway. Of course, red yellow and white "T"  aspects and
arrows are used at junctions in street track.

The four tramway-railway level crossings in Melbourne were protected on the
tramway approaches by disc signals and catchpoints. The disc signals have
(all?) been replaced by colour-light signals. The crossings are all
controlled from an adjacent signal box, and a big switch linked to the booms
switches the overhead between the tramway 600 volts and the railway 1500
volts (that failed once, too - a tram went into the crossing with 1500 volts
on the overhead - went very fast for a short while, then very slowly to the
workshops!)

ATB was tried in Sydney over the (previous) Iron Cove Bridge. Not because it
was single line, but because the track centres were too close for opposing
cars to pass.

I've never heard of any other street tramway using OTS&T or anything like
it. Theoretically, the single line which used to form the last half
kilometre of the Carnegie route in Melbourne was protected by a staff, but,
in many, many trips on that line, I never saw it! It was worked, in
practice, by sight/timetable.

Sydney actually had a staff section comprising the curve from Cleveland St
into Crown Street!!!! I don't know if tickets were issued!


Rgds

Ron BEST
Barry Campbell wrote in message <36CCBB8D.ABF6A7FD@qimr.edu.au>...
>Ron BEST wrote:
>>
>> Recent posts on this subject remind me of the practice mentioned in  one
of
>> David Keenan's excellent books about the Sydney (2nd generation) tramway
>> system ("The North Sydney Lines"):
>>
><snip>
>>
>> The system was "formalized" in later years by provision of a dial and
>> pointer system.
>
>The Sydney & Newcastle electric systems were controlled until the 1930's
>by a branch of the railway dept and kept some railway characteristics to
>the end. OTS&T working on single lines was one of them. Does anyone know
>how other systems coped with single lines and other such railway things
>such as complicated junctions.
>
>
>Barry Campbell