The document discusses improving safety at user worked crossings through technical and human factors approaches. It summarizes lessons learned from Swiss trials which showed users understood red lights but not the absence of lights. It then outlines Network Rail's requirements, including a minimum of red lights and audible signals. The VaMoS technical approach is presented, using red and green lights with just-in-time warnings to create an unmistakable user interface. Safety requirements are discussed, mandating fail-safe light indications and train detection. Lower system costs can improve safety by allowing more widespread installation and use of alternative power sources without maintenance issues.

1. 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

2. Value for Money Systems
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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3. Value for Money Systems
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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4. Value for Money Systems
2 Experience from Swiss Trial
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5. Value for Money Systems
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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6. Value for Money Systems
3 Network Rail Requirements
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7. Value for Money Systems
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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8. Value for Money Systems
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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9. Value for Money Systems
4 VaMoS: Technical approach
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10. Value for Money Systems
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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11. Value for Money Systems
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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12. Value for Money Systems
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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13. Value for Money Systems
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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14. Value for Money Systems
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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15. Value for Money Systems
7 Conclusion
"Assumed" value
of violation
Associated price
of violation
Old
Gain of time
=
high value
Little risk awareness
=
low price
New
No gain of time
=
small value
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Decision
Violation is
assumed being
beneficial
Red light means danger Waiting
=
is beneficial
high price
07.03.2014

16. Value for Money Systems
Questions?
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07.03.2014