Re: Glenbrook train was travelling about 37kmh at time of crash: expert

[David Johnson <trainman@ozemail.com.au>]

"C. Dewick" wrote:

> "Gnome 412" <gnome412@hotmail.com> writes:
>
> >from http://www.smh.com.au/breaking/0003/21/A21846-2000Mar21.shtml today ...
>
> >Source: AAP | Published: Tuesday March 21, 12:07 PM
>
> >The commuter train involved in the Glenbrook disaster was travelling at an
> >estimated speed of 37kmh when it hit the Indian Pacific, a British expert
> >said today.
>
> >Kevin Thomas Crofts, a mechanical engineer who has worked for 20 years
> >studying the structural integrity of trains was brought out to Australia
> >from Derby, England to examine the aftermath of the December 2 collision.
>
> >The collision near Glenbrook in the New South Wales Blue Mountains left
> >seven people dead and 51 injured.
>
> >Mr Crofts told the inquiry into the crash he used five factors to estimate
> >the speed of impact: the extent of the damage, the gradient of the track,
> >the braking performance of the interurban train, the time delay between the
> >driver applying the brakes and them coming into effect and the reaction time
> >of the driver.
>
> But he forgot to take into account the environmental conditions around the
> track in the cutting which may have a critical effect on the braking
> performance of the train.
>
> I still stand by my original claim that it is *impossible* without intensive
> analysis (and five factors do not make for intensive analysis) of everything
> involved.
>
> And regardless of what Mr Crofts has determined, even he has said it's an
> 'estimated' speed. I guess it's probably the best official estimate we'll
> get.
>
> We can safely assume that there would have some speed reduction prior to
> impact owing to the time which elapsed between the driver leaving the
> controls in emergency braking (either by actual moving the brake handle to
> 'emergency', or by releasing the master controller handle, or both) and
> getting out of the cab into the main body of the car.
>
> So this raises the next question - if Mr Crofts says the train was estimated
> as doing 37 kph when it hit the IP, how does he know for certain what the
> speed vs distance curve was for the few seconds between the driver of the
> intercity train becoming first aware (ie. when his brain processed the
> visual information about the IP in front and started the neural processes
> off to take the necessary physical actions) and when the train actually
> collided with the IP?
>
> He doesn't.
>
> >If the interurban driver reacted 0.4 of a second after seeing the Indian
> >Pacific on the track ahead of him, and the Indian Pacific was travelling at
> >6kmh Mr Crofts said the impact speed was in the range of 34-41kmh.
>
> 0.4 seconds is pretty fast don't you think? Most people have an average
> reaction time of between 0.7 and 1.5 seconds depending on their level of
> alertness, etc. so I find the figure of 0.4 seconds extremely optimistic.
>
> >'The most probable actual velocity was probably around 37kmh,' he told the
> >special commission of inquiry into the crash.
>
> >Mr Crofts said the interurban train was likely to have been travelling at a
> >speed of 53.5kmh when the driver first spotted the Indian Pacific ahead of
> >him.
>
> Ah - here we are... Ok, so the train is claimed to have reduced speed from
> 53.5 kph (14.86 m/s) to 37 kph (10.27 m/s) between when the emergency brake
> was applied and when the two trains hit. Over what distance did the
> intercity train travel between these two points? I would estimate, given the
> grade, etc. that the maximum deceleration under emergency conditions would
> not be more than about 0.6 m/s/s. Does anyone have accurate data that can be
> used to do some test-calculations?
>
> Sounds quite unlikely that the train could have been doing anywhere near 50
> kph, or else the distance required to reduce speed to 37 kph would be a lot
> larger than the actual distance involved in this incident unless the rails
> were totally dry and the train didn't skid or slip once the emergency brakes
> were fully applied.
>
> >He said the damage was intensified because the Indian Pacific's last
> >carriage, a car carrier, and the interurban carriage were of different
> >structures.
>
> Well what's so unusual about that? It's not something we didn't already now
> by simple observation. 8-)
>
> >Very little of the energy of the crash was absorbed by the Indian Pacific
> >car carrier.
>
> Once again, we already knew that.

Just speculating, but after the 3801 accident on 6/5/90 at Cowan, all wooden
bodied stock were required to be fitted with anti-telescoping bars.  If these
bars had been fitted to the car carrier and the V set, I wonder if this accident
would have been anywhere near as bad?

--
David Johnson
trainman@ozemail.com.au
http://www.ozemail.com.au/~trainman/
------------------------------------
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