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Session 48 Johan Engström
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Session 48 Johan Engström

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  • 1. Hur leder kritiska händelser till allvarliga olyckor? Johan Engström, Volvo Technology Transportforum, Linköping 2011-01-13
  • 2. Accidents and incidents p
  • 3. Intro
    • Key questions:
      • How do normal driving develop into critical events?
      • How do critical events develop into crashes?
    • Traditionally: Limited data to answer these questions (crash reconstruction, subjective reports)
    • Today
      • Naturalistic data with real crashes and near-crashes captured on video
      • Need to know what to look for – need for an accident model for micro-level analysis of the pre-crash phase
  • 4. Anticipatory selection in driving
    • Driving involves proactive selection of relevant information and actions
    • Based on expectations on how an upcoming situation will develop
    • Can be conceptualised in terms of schemata
  • 5. Schemata
    • Functional representations of actions, or action sequences making up a task
    • Embody ”implicit” expectations
    • Learned with experience
    • Overlearned schemata often selected and excecuted automatically without conscious awareness, even at task level (”zombie behaviour”)
    • Schema selection = attention selection
    Turn right at intersection Look left for cars Slow down Turn right Task context schema Basic schemata
  • 6. Attention/action selection model
    • Task context and basic schemata
    • Related schemata may compete for activation
    • Schemata selected top-down (proactively) and/or bottom-up (reactively)
    • Two types of top-down selection
      • Context-driven (automatic, unconscious, inflexible)
      • Cognitive control (effortful, conscious
    Schemata Environment Sensing Actuation Schemata Basic Task context Cognitive control Schemata Task context Top-down Bottom-up
  • 7. Critical situations
    • Critical situations occur due to a conflict between the proactively selected schema and how the actual situation develops
    Schemata Environment Sensing Actuation Schemata Look for pedestrians Task context Cognitive control Schemata Drive through intersection Top-down
    • Possible reasons:
      • Infrequent event
      • Misleading traffic/infrastructure configuration
      • Attentional ”capture” of competing schema (distraction)
      • Unfamiliarity
      • Working memory load
      • … .
  • 8. How do critical situations lead to crashes?
    • Possible reasons:
      • Insufficient time to react
      • Stimulus outside field of view (e.g. due to off-road glance)
      • Blink
      • Occlusion
      • Change blindness
      • Glare
      • Low stimulus saliency
      • Microsleep
      • … .
    A critical situation will lead to a crash if last-second, reactive schema selection fails Schemata Environment Sensing Actuation Schemata Brake! Task context Cognitive control Schemata Drive through intersection Top-down
  • 9. A general accident model Normal driving Critical event Crash Schema Situation Conflict ? Successful bottom-up selection? No Near crash time Reactive barrier Proactive barrier Yes No Yes
  • 10. Real world example 1: Car-bicycle crashes at intersections and roundabouts (Summala and Räsänen, 2000)
  • 11. Interpretation – Summala study Driver’s schema: Look for cars to the left Bottom-up selection: None since the bicyclist appears outside the field of view Actual situation Bicyclist approaching from the right Normal driving Critical event Crash Conflict ? No Reactive barrier Proactive barrier Yes
  • 12. Real-world example 2: Rear-end crash in the 100-car study Narrative (by VTTI analyst): Subject driver is approaching a right turn at an intersection. The lead vehicle briefly stops at stop sign, then moves forward as if completing the turn. As the subject driver looks out his left window to check traffic, the lead vehicle stops again. The subject vehicle hits the lead vehicle in the rear. Inopportune glance. Event 8633 Brake Gaze Speed Impact Acceleration
  • 13. Interpretation – 100 car rear end crash (event 8633) Driver’s schema: Lead vehicle will continue to turn -> OK to look left to check traffic Actual situation Lead vehicle stops again Bottom-up selection: None since the lead vehicle braking occurs outside the field of view Normal driving Critical event Crash Conflict ? No Reactive barrier Proactive barrier Yes
  • 14. Aggregate analysis, 8 rear-and crashes Homogenous mechanisms!
  • 15. Aggregate analysis, 8 near crashes More heterogenous mechanisms!
  • 16. Lee et al. (2007) quantitative analysis of 100-car study rear end events (same data) Eyes-off-road is what distinguishes the crashes TTC similar between crashes and near crashes
  • 17. Some implications
    • Hard to define ”crash-relevant events” in pure kinematic terms
    • Data on driver’s proactive schema selection ideally requires both video and subjective report
    • However, proactive selection often unconscious -> drivers may not be able to report! (aneqdotal data from Hanowski)
  • 18. Conclusions
    • A critical situation occur due to a mismatch between the proactively selected schema and how the actual situation develops -> breaking proactive barrier
    • A critical event will lead to a crash if last-second, reactive schema selection fails -> breaking reactive barrier
    • Accident/incident analysis at micro level should find out key mechanisms behind breaking of proactive and reactive barriers
    • Requires combination of naturalistic and laboratory (simulator) data
    • Future goal: Coherent taxonomy and classification scheme

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