On Sep 7, 8:46*pm, Chris Tolley wrote:

Mizter T wrote:
A bus swerving to avoid a car would appear to be the genesis of the
accident. ... *if* (and that is a big if) the traffic signals had in
some way malfunctioned then things would become more interesting
given the interface between highway and tramway signalling.

I don't follow your reasoning. If the genesis of the accident is a bus
swerving to miss a car, then I can't see that the tram's signalling is
in any way implicated.


Sorry, I didn't make myself clear. In Croydon, as is the case
elsewhere with other tram systems, the highway traffic control signals
are linked in to the tram's signalling system so as to enable trams to
negotiate a variety of road junctions - this evidently requires a more
complex set of interlinking/interoperability (or even 'interlocking'
as it were) between the highway signals and the tram network's
signalling system. On top of that one can assume that at least some of
the highway signals in the area are co-ordinated with each other as
part of a traffic management setup (as I'm sure is the case in central
Croydon).

*If* the highway signals (indeed and the tram signals) had
malfunctioned then this could have caused or contributed towards the
car and/or bus (indeed and/or tram) being in the wrong place, hence
the relevance of this factor.

The reason I even mentioned signalling in the first place was the
'Croydon Today' article contained the suggestion, made by a witness,
that traffic lights might have been at fault - but one should note
that this is by no means verified information.

For the record, because local newspaper websites do get rejigged with
some regularity, here is a pertinent extract from the 'Croydon Today'
article:

quote
Road sweeper Martin Storm, 54, from Church Street, Croydon, who saw
the crash, said:
"The bus was coming up Park Street and swerved to avoid a car which
was coming down Wellesley Road.
"The bus driver swerved left to avoid the silver car. The bus driver
tried to avoid everything, but he couldn't avoid it.
"The car has got stuck between the tram stop and the bus and was
crushed.
The driver of the tram was really upset, but it wasn't their fault. I
was behind it all, there was blood everywhere."
He added: "The police told me the traffic lights had failed and were
all on green."
However while saying the traffic lights was one area which would be
looked at during the investigation, police today did not confirm they
had not been working.
/quote

Source:
http://www.thisiscroydontoday.co.uk/...l/article.html

Mizter T wrote:

On Sep 7, 8:46*pm, Chris Tolley wrote:

Mizter T wrote:
A bus swerving to avoid a car would appear to be the genesis of the
accident. ... *if* (and that is a big if) the traffic signals had in
some way malfunctioned then things would become more interesting
given the interface between highway and tramway signalling.

I don't follow your reasoning. If the genesis of the accident is a bus
swerving to miss a car, then I can't see that the tram's signalling is
in any way implicated.


Sorry, I didn't make myself clear. In Croydon, as is the case
elsewhere with other tram systems, the highway traffic control signals
are linked in to the tram's signalling system so as to enable trams to
negotiate a variety of road junctions - this evidently requires a more
complex set of interlinking/interoperability (or even 'interlocking'
as it were) between the highway signals and the tram network's
signalling system. On top of that one can assume that at least some of
the highway signals in the area are co-ordinated with each other as
part of a traffic management setup (as I'm sure is the case in central
Croydon).

*If* the highway signals (indeed and the tram signals) had
malfunctioned then this could have caused or contributed towards the
car and/or bus (indeed and/or tram) being in the wrong place, hence
the relevance of this factor.

Okay, that's clearer. Thanks.

--
http://gallery120232.fotopic.net/p9632771.html
(20 077 at Buxton, Jun 1985)

On Sun, 7 Sep 2008 14:28:56 -0700 (PDT) someone who may be Mizter T
wrote this:-

Sorry, I didn't make myself clear. In Croydon, as is the case
elsewhere with other tram systems, the highway traffic control signals
are linked in to the tram's signalling system so as to enable trams to
negotiate a variety of road junctions

The tramway signalling system [1] makes a request to the traffic
light controller. The request informs the traffic light controller
that a tram is approaching or waiting depending on circumstances.
How the traffic light controller responds to this request depends on
the junction and the circumstances at the time. At one extreme it
will respond immediately and change the other lights before giving a
proceed signal to the tram driver. At the other extreme it will note
the tram request and fit it in when a suitable opportunity arises.

The priority of a tram request may be increased if the tram comes to
a stand at the junction. It all depends on the junction and how that
is linked to other (road) junctions.

Many road junctions may be linked and the road bods may not give
trams absolute priority. However, trams are carrying many people in
a small amount of road space and thus can be given a high priority
than other forms of traffic.

[1] generally just detector loops. An advance detector is placed
some way in the rear of the signals. A stop detector is placed at
the stop mark. A cancel detector is placed after the lights, if the
proceed signal has not already been replaced by the white dot then
this detector will initiate this. One detector can perform more than
one function, for example a cancel detector can also function as the
advance detector for signals further along the tramway.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54