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Accident at Hockham Road level crossing, Norfolk, 10/04/2016

Discussion concerning level crossings

Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby AndyB » Sat Jul 23, 2016 4:34 pm

LlaniGraham wrote:
AndyB wrote:Graham, if they have a red light, they have a power supply.


None of the UWC's I controlled had red lights, therefore they had no power to them. Likewise the Boxes either side of mine.
I suspect that the majority of UWC's don't have power to them.

Point spectacularly missed!

However, for your benefit, and to repeat myself...
I wrote:However, I don't really understand why UWC can't have gates locked with the signals in such a way that if the gates are closed or the barriers are down they stay that way if the light is red. I fully understand not wanting barriers to descend automatically due to escape routes, subject to timeouts.

If the crossing doesn't have a red light, there is nothing to interlock the gates with, so I would have thought it was pretty blindingly obvious that I wasn't referring to crossings without miniature warning lights.

To repeat the point I was making before you threw up the straw man of UWCs without red lights, I do not understand why UWCs with miniature warning lights cannot have the gates locked when the light is red.
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby StevieG » Sat Jul 23, 2016 10:19 pm

AndyB wrote: " .... To repeat the point I was making before you threw up the straw man of UWCs without red lights, I do not understand why UWCs with miniature warning lights cannot have the gates locked when the light is red. "
Do all such 'red light' UWCs have separate pedestrian gates ?
Else would one reason not to lock gates when the 'signals' are red, be that someone crossing when the lights went green-to-red would be 'locked in' ?
BZOH

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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby AndyB » Sat Jul 23, 2016 10:51 pm

Good thinking. Given that pedestrians are just going to open and close the gates as they pass through, an emergency release would be required - say a green "press to exit" type button accessible only from the rail side of the gates.
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby StevieG » Sat Jul 23, 2016 11:21 pm

.... there can be more to level crossing design than might be apparent at first.
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby John Hinson » Wed Jul 27, 2016 7:49 pm

I have removed some posts.

Those wishing to pursue their differences should do so by PM rather than making themselves look stupid in public.

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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby Mike Stone » Tue Mar 14, 2017 11:51 am

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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby Andrew Waugh » Wed Mar 15, 2017 10:47 am

Having read the report, two immediate observations spring to mind...

1) Why on earth are Network Rail reinventing the wheel with level crossing protection? There are any number of off-the-shelf level crossing controllers used in the US which could be used to drive a UWC. (A subsidiary question: why on earth are they persisting with requiring to push a button to get the indication? This has obvious risks. The power consumption of LEDs is so low that there would seem to be no barrier to continuous display of the indication.)

2) As a professional programmer, and one interested in user interface design, I would have to say that I think the Thetford workstation displays are diabolically poor. The most common task of the signaller using this workstation is to decide whether a caller can cross the line. This is a safety critical task. But *no* special support is given to the signaller in performing this task. Worse, the screen is cluttered with indications and controls that are probably rarely used - the lockout indications, and the status of the MCB-OO crossings, for example. No wonder the some of the signallers disliked using it.

You'd have your work to convince me that any task based analysis had been carried out in the user interface design. To be brutally honest, it looks like the designers simply replicated a panel, and squashed it all up to get the maximum length on one screen.
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby AN106 » Wed Mar 15, 2017 1:56 pm

Andrew Waugh wrote:A subsidiary question: why on earth are they persisting with requiring to push a button to get the indication? This has obvious risks. The power consumption of LEDs is so low that there would seem to be no barrier to continuous display of the indication.

There are some advantages for the push button configuration:

1) In the event of an incident, it's possible to prove whether or not the user pressed the button (thereby drawing their attention to the lights), or simply crossed without bothering. In an "always on" configuration there's no proof that the user looked or not.

2) Audible alarms are muted when the button hasn't been pressed, reducing noise for local residents

3) Even though the consumption is low, it is still high enough to be a significant drain where power supplies are limited (e.g. from a solar-wind generator)
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby Andrew Waugh » Thu Mar 16, 2017 12:34 am

Andrew Waugh wrote:Having read the report, two immediate observations spring to mind...
2) As a professional programmer, and one interested in user interface design, I would have to say that I think the Thetford workstation displays are diabolically poor. The most common task of the signaller using this workstation is to decide whether a caller can cross the line. This is a safety critical task. But *no* special support is given to the signaller in performing this task. Worse, the screen is cluttered with indications and controls that are probably rarely used - the lockout indications, and the status of the MCB-OO crossings, for example. No wonder the some of the signallers disliked using it.

You'd have your work to convince me that any task based analysis had been carried out in the user interface design. To be brutally honest, it looks like the designers simply replicated a panel, and squashed it all up to get the maximum length on one screen.


I spent the night thinking about this, and my bewilderment only increases.

Network Rail spent quite a bit of time (and resources) investigating and managing the problem that the EBI Gate was really only designed to SIL1, not the required SIL3. Even at SIL1, however, the EBI Gate was only expected to generate "an incident and unsafe mode between 10 and 100 years". Eventually, they turned the installations off because it did not meet the required safety level.

In my view (remember, I'm speaking as a professional software engineer), the incidence of a signaller making a mistake due to the poor GUI design is far more likely than once every 10 and 100 years. Indeed, a serious incident occurred after only 4 years of use of the GUI (and we don't know if other "incidents and unsafe modes" had previously occurred, but not resulted in a reportable accident).

There seems to be a lack of proportionality in the two responses; Network Rail focused their attention on the *less* likely cause of accidents.

Interestingly, the RAIB also seem to be oblivious to this issue. The poor GUI design is relegated to an additional observation (Para 127), and they never explicitly consider the relatively likelihood of failures of the various components of the system. Note also Recommendation 2 (Para 140) - mistakes by signallers are to be addressed by more training to ensure they achieve and maintain competency. There is no consideration that an alternative approach is to improve the GUI to support the signaller in performing their tasks and reduce the likelihood of making mistakes.

I wonder how much expertise the RAIB has in identifying software risks?
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby Stuart Johnson » Thu Mar 16, 2017 2:33 pm

Andrew Waugh wrote:[
Interestingly, the RAIB also seem to be oblivious to this issue. The poor GUI design is relegated to an additional observation (Para 127), and they never explicitly consider the relatively likelihood of failures of the various components of the system. Note also Recommendation 2 (Para 140) - mistakes by signallers are to be addressed by more training to ensure they achieve and maintain competency. There is no consideration that an alternative approach is to improve the GUI to support the signaller in performing their tasks and reduce the likelihood of making mistakes.

I wonder how much expertise the RAIB has in identifying software risks?

Plenty, thanks. The decision to decommission the EBI Gate equipment was examined closely during the investigation. The context is given by the last sentence of paragraph 98:
However, witness and documentary evidence show that no resolution was achieved, and the business relationship between the two companies deteriorated.

The events which followed led inexorably to the decision that was eventually taken, and which was supported by the safety regulator (paragraph 104). Everyone concerned was convinced that they were doing the right thing, and had professional advice to back up their view.

I would not, however, disagree with your view of the relative risks of the two approaches. :(
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby beast66606 » Fri Mar 17, 2017 9:33 am

I hope the expertise examining the circumstances surrounding the accident was higher than those who labelled the accident site on page 9 of the report where Roudham Hall crossing has been incorrectly marked as the accident site.
Better to be thought a fool than to type a response that confirms it.

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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby Signal-sighter » Fri Mar 17, 2017 10:14 am

It is possible to configure the EBI Gate 200 for the lights to be permanently illuminated rather than 'on demand' where particular circumstances warrant it - in those instances the button is replaced with a blanking plate.
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby Stuart Johnson » Fri Mar 17, 2017 12:11 pm

beast66606 wrote:I hope the expertise examining the circumstances surrounding the accident was higher than those who labelled the accident site on page 9 of the report where Roudham Hall crossing has been incorrectly marked as the accident site.

Thanks (again) for spotting that (the first person to do so, despite draft copies going to all the industry bodies involved for consultation!). Our apologies for the mistake, and the online report has now been corrected.
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Re: Accident at Hockham Road level crossing, Norfolk, 10/04/

Unread postby beast66606 » Fri Mar 17, 2017 4:39 pm

Hi Stuart,

Just seen your comments elsewhere - thanks.
Better to be thought a fool than to type a response that confirms it.

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