daniel berchtold, head business unit rail automation, schweizer electronic
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Increasing Safety at User Worked Crossings – How can Human Factors be Considered in a Technical Approach
Daniel Berchtold Head Business Unit Rail Automation Schweizer Electronic
07.03.2014
Value for Money Systems
Carefree Signalling Solutions
Contents
1. Summary of relevant Human Factors on LX
2. Experience made during Swiss Trial
3. Network Rail requirements for EUWC
4. VaMoS: Technical Approach
5. Resulting safety requirements
6. How does cost influence safety?
7. Conclusion
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1 Human Factors on LX
Unconscious failure
– Distraction / Fatigue / Habit
– Misunderstandings
– Unclear situation / unclear indication
Conscious failure
– Violation => avoiding waiting time
– Wrong decision making => unawareness of risks
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2 Experience from Swiss Trial
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2 Experience from Swiss Trial
Red light well understood – absence of red light was not
Instructions were rarely read
Language problem
Uncertainty on persistent “Dark signal”
“No Red” was quickly associated with “No Train”
Waiting time was crucial
On-Call function was accepted/understood
Trust in system when indication clear and just-in-time
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3 Network Rail Requirements
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3 Network Rail Requirements
Minimum: Red Light & audible signal
Minimize warning time
Clear user interface / independent from user language
SIL 1
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4 VaMoS: Technical approach
1. Road User Interface: Red and Green light
2. Just-in-time warning: 10/20 secs
3. No instructions / unmistakable user indication
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4 VaMoS: Technical approach
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4 VaMoS: Technical approach
Road User Interface
Well known principle (code of practice) – Green: GO
– Red: STOP
– Dark: Not in operation
Broadly understood (children, foreigners)
Fail-safe principle
Audible warning
No instructions
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4 VaMoS: Technical approach
Train Detection
Frauscher RSR123 wheel detection – Fail-safe, reliable
– Maintenance free
– Exact train position
– Well proven
Just-in-time warning
Simple and easy to install
No interference with existing systems
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5 Resulting Safety Requirements
Red and especially Green light indication MUST be fail-safe
– Failed Red => increased risk for user
– Failed Green => immediate danger
– Risk based approach => SIL 3 like regular LX
Train indication and approaching time MUST be fail-safe
Much higher system availability
– Dark mode = increased risk
Automatic, reliable, remote failure indication
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6 How does cost influence safety ?
The lower the cost, the quicker and higher number of systems will be installed
Minimized power consumption => allows cost effective alternative power supplies
No maintenance => high maintenance cost is often an obstacle to install additional systems on a network
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7 Conclusion
A fail-safe and reliable system with just-in-time warning combined with an unmistakable user interface remarkable reduces risk due to human misbehaviour
Red light is associated with immediate danger rather than just “waiting time”.
Supports “safe” decision making of the road user:
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7 Conclusion
"Assumed" value of violation
Associated price of violation
Decision
Old Gain of time =
high value
Little risk awareness =
low price
Violation is assumed being beneficial
New No gain of time =
small value
Red light means danger =
high price
Waiting is beneficial
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Questions?