Mental load of the
Westerschelde tunnel operator
TNO Human Factors
Drs. Jouke Rypkema
TNO Human Factors
P.O Box 23
3769 ZG Soesterberg
+31 346 356322
[email protected]
Westerschelde motor-traffic tunnel:
location
Mental load of the Westerschelde tunnel operator
Human Factors
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Westerschelde motor-traffic tunnel:
details
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6.6 km long
2 tubes, each tube 2 driving lanes
Evacuation corridors every 250 m
Cameras every 150 m
20 monitor displays
Sensors (e.g. traffic speed, vehicle height, sight)
Controllers (e.g. traffic lights, speed reduction signs)
One operator to guard the tunnel
Mental load of the Westerschelde tunnel operator
Human Factors
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Question:
Can the tunnel be controlled safely by
one tunnel operator?
Mental load of the Westerschelde tunnel operator
Human Factors
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Cognitive load analysis
• Is the operator capable to (cognitively) perform his or
her tasks?
Mental load of the Westerschelde tunnel operator
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3D cognitive load model
Mental load of the Westerschelde tunnel operator
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Scenarios
• Five scenarios were analysed
• Some severe (for example, accident with bus that
catches fire)
• Some more common (for example, car without fuel
standing still in tunnel)
Mental load of the Westerschelde tunnel operator
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Scenarios: method analysis
Time
System
(TUBES)
Operator
Event
Bus hits car and
catches fire,
two lanes blocked
0
1
5
Notification
(auditory/visual)
Detection on
MMI
5
5
Autostart ventilation
(after 60s)
35
Auto CCTV selection
Build-up
internal image
30
35
Perform calamity
procedure
Press calamity
button
0
Mental load of the Westerschelde tunnel operator
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Results
• Time occupied always high (vigilance)
• Overall, average cognitive load acceptable, but
• Cognitive load is extremely high for three scenarios
during period just after incident
1
0 - 675
100
52
13
2
0 - 1105
100
54
12
3
0 - 920
100
23
10
52
92
92
Mental load of the Westerschelde tunnel operator
Critcal period
Scenario
Time (in sec)
Time occupied (in %)
Complexity (in %)
Task-set switches
(number)
Task-set switches
(average time between
switches)
Human Factors
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Results (2)
2
Level of
information
processing
3
23
1
4
1
5
Time occupied
Task-set switches
Mental load of the Westerschelde tunnel operator
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Conclusions
Cognitive load too high at the start of incidents, because:
• Too many tasks in short time (especially with evacuation)
• Tasks too complex because lack of (clear) procedures
• Sometimes number of task-set switches too high as a
result of intertwined task-sets
And:
• Sudden change from monotonous vigilance task to
highly demanding crisis situation
• Responsibility until emergency services arrive
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Recommendations
• Develop / improve procedures related to categories of
incidents.
• Develop evacuation procedures. Pay attention to
communication and guidance.
• Improve procedures for communication with third
parties. Restrict communication tasks during crisis
situations.
• Cluster the operator tasks in sets.
• Provide a second person for assistance during crisis
situations.
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Recommendations training
• Train “on the job” for normal situations.
• Use a simulator to train for critical situations.
• Repeat training frequently (3-6 monthly).
• Organize interdisciplinary training with emergency
services.
Mental load of the Westerschelde tunnel operator
Human Factors
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Thank you for your attention
For more information contact:
Jouke Rypkema
[email protected]
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Human Factors
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