Re: Safety first in rail system's radical revamp

[signal_spotter@my-deja.com]

In article <ZKLO5.22474$SF5.451867@ozemail.com.au>,
  "John Kerley" <deaftech@ozemail.com.au> wrote:
>
> <signal_spotter@my-deja.com> wrote in message
> 8udaqi$ka$1@nnrp1.deja.com">news:8udaqi$ka$1@nnrp1.deja.com...
> > We have the expertise right here in Australia to install an ATP
system.
> > See
http://www.westsig.com.au/DEPT/Marketing/common/datasheets.nsf/Data%
> > 20Sheets?OpenView&Start=1&Count=30&Collapse=1#1 for details (Look
under
> > Control systems). An interesting point is that the UK are in the
middle
> > of a debate (see uk.railway newsgroup) about whether to continue
with
> > ATP or put in a lesser (but still as safe) system called TPWS (Train
> > Protection Warning System) which basically is the magnetic
equivelant
> > of trainstops and Intermediate trainstops. The pollies don't need
to go
> > on a 'fact finding' mission. They only have to consult the experts.
> >
> > regards Ian
> >
> >
> > Sent via Deja.com http://www.deja.com/
> > Before you buy.
>
> Is TPWS really "still as safe" as ATP? If so, why the furore over
installing
> TPWS instead of ATP in Britain?
> You can still travel a long way past a SPAD after being "tripped" at
line
> speed.  Whilst TPWS is a little more sophisticated than that, it
still does
> not provide the more continuous speed monitored control that I
understand
> ATP does.
>
TPWS not only provides trip braking should a train SPAD (ala trainstop)
but it also incorporates a speed check before the signal and if the
train is travelling too fast ie high probability of a SPAD, then the
brakes are tripped (ala Intermediate Trainstops). So the incidence of
SPADs are reduced. In terms of safety, the improvement that ATP has
over TPWS, is that the human error factor is reduced. System wise they
are both safe, but when you add human error into the equation then ATP
is "safer". However any railway (including India's notorious system) is
still safer than the roads.

regards Ian
> Having said that,  on a "cost - benefit", or "cost per fatality
prevented"
> basis TPWS is probably a reasonable choice when compared to the cost
> prepared to be spent of accident reduction measures on the road, or
more
> relevantly, the lack of cost.  Cars  have no speed control or SPAD
> prevention devices.
>
> It is interesting that the Brits did not adapt their magnetic AWS
devices to
> be SPAD "trips" on mainline tracks many years ago, given that like
Melbourne
> and Sydney electrified suburban lines, the tube has had mechanical
trips
> since early this centuary. It almost certainly would have prevented
the
> Ladbroke Grove accident.
>
> Cheers,
>
> John Kerley
>
>


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