Fundamental probabilistic analysis analysis Fundamental probabilistic on effectiveness on effectiveness of safety- -presentation type presentation type of safety on safe driving support system on safe driving support system ○ K. OKABE, M. KAMATA ○ K. OKABE, M. KAMATA (Tokyo (Tokyo Univ Univ. JPN) . JPN) T. HIRAOKA, H. KUMAMOTO (Kyoto Univ Univ. JPN) . JPN) T. HIRAOKA, H. KUMAMOTO (Kyoto 1
Current Situation Current Situation � Traffic road accidents in Japan � Traffic road accidents in Japan � About 10,000 people are killed (decreasing) � About 10,000 people are killed (decreasing) � About 1,000,000 people are injured (increasing) � About 1,000,000 people are injured (increasing) ⇒ AHS( Advanced Cruise ) AHS( Assist Highway System ) Advanced Cruise- -Assist Highway System � Seven support services � Seven support services - Necessity of quantitative assessments Necessity of quantitative assessments - 2
Source: Ministry of Land, Infrastructure and Transport 3
Seven Services of AHS Seven Services of AHS � Prevention of collision with forward obstacles � Prevention of collision with forward obstacles � Prevention of overshooting on curve � Prevention of overshooting on curve � Prevention of lane departure � Prevention of lane departure � Prevention of crossing collisions � Prevention of crossing collisions � Prevention of right turn collisions � Prevention of right turn collisions � Prevention of collisions with pedestrians � Prevention of collisions with pedestrians crossing streets crossing streets � Road surface condition information for � Road surface condition information for maintaining headway,etc maintaining headway,etc 4
Safety Analysis Safety Analysis � Safety alarm for forward obstacle curve collision � Safety alarm for forward obstacle curve collision � Road � Road- -Vehicle communication system Vehicle communication system Wireless STOP STOP 5
Discussion Point Discussion Point � Configuration of safety monitoring system � Configuration of safety monitoring system � Fault warning type � Fault warning type & & Safety presentation type Safety presentation type Safety Fault Warning Presentation Danger ! Safe ! GO STOP Which is more appropriate? 6
Comparative Study Comparative Study � Evaluation of implementation effect � Evaluation of implementation effect � Possibility of decreasing accidents (normal operation) � Possibility of decreasing accidents (normal operation) � Scarcity of � Scarcity of increasing accidents (abnormal operation) increasing accidents (abnormal operation) => Probabilities of fail dangerous failure Safety Fault Warning Presentation No obstacle Obstacle ! Safe Danger ! GO STOP 7
Accident Outbreak Accident Outbreak � Definition of the process � Definition of the process A : : Avoidance Action Avoidance Action A Ex. stopping, changing lane : No Avoidance Action No Avoidance Action A : A Ex. keeping on driving D : : Presence of Dangerous Relation Presence of Dangerous Relation D Def. situation where A surly cause accident 8
Fail Dangerous Failure Fail Dangerous Failure � Fault warning � Fault warning � Sensor fails to detect a danger relation � Sensor fails to detect a danger relation D D � Sensor succeeds in � Sensor succeeds in detecting detecting D D but fails to send a message but fails to send a message � Safety presentation � Safety presentation � Sensor � Sensor fails to detect fails to detect D and sends false message false message D and sends Fault Warning Safety Presentation Danger ! Safe ! 9
Fail Dangerous Probability Fail Dangerous Probability � Reliabilities � Reliabilities QuickTime?and a � Sensor detection Photo - JPEG decompressor � are needed to see this picture. Sensor detection QuickTime?and a Photo - JPEG decompressor QuickTime?and a are needed to see this picture. Photo - JPEG decompressor are needed to see this picture. � Communication � Communication QuickTime?and a are needed to see this picture. Photo - JPEG decompressor � Fault warning � Fault warning � Sensor fails to detect a danger relation � Sensor fails to detect a danger relation D D QuickTime?and a Photo - JPEG decompressor are needed to see this picture. � Sensor succeeds in � Sensor succeeds in detecting detecting D D but fails to send a message but fails to send a message QuickTime?and a Photo - JPEG decompressor are needed to see this picture. � Safety presentation � Safety presentation � Sensor � Sensor fails to detect fails to detect D and sends false message false message D and sends QuickTime?and a QuickTime?and a Photo - JPEG decompressor Photo - JPEG decompressor QuickTime?and a Photo - JPEG decompressor are needed to see this picture. are needed to see this picture. are needed to see this picture. 10
Study Result #1 Study Result #1 � Evaluation of implementation effect � Evaluation of implementation effect � Possibility of decreasing accidents (normal operation) � Possibility of decreasing accidents (normal operation) � Scarcity of � Scarcity of increasing accidents (abnormal operation) increasing accidents (abnormal operation) => Probabilities of fail dangerous failure Safety Fault Warning Presentation is more appropriate No obstacle Obstacle ! Safe Danger ! GO STOP 11
Comparative Study Comparative Study � Evaluation of implementation effect � Evaluation of implementation effect � Possibility of decreasing accidents (normal operation) � Possibility of decreasing accidents (normal operation) � Scarcity of � Scarcity of increasing accidents (abnormal operation) increasing accidents (abnormal operation) =>Estimated Accident Probability after Implementation Safety Fault Warning Presentation No obstacle Obstacle ! Safe Danger ! GO STOP 12
Accident process Accident process � Event � Event Tree Tree Dangerous relation Driver action No accident D A D A Accident Message Message ： How does it change ? ： A A How does it change ? No accident D D : Avoidance Action D : Presence of Dangerous Relation : Presence of Dangerous Relation A : Avoidance Action A D : No Avoidance Action A : No Avoidance Action : Non- -Presence of Dangerous Relation Presence of Dangerous Relation A D : Non D 13
Effect of Message Effect of Message Fault warning type Action Dangerous relation Message D D A A STOP STOP Success zZZ A A Fail Safety presentation type Accident Dangerous relation Action Message D D A A zZZ Success Fail Go Go A A 14
Effect of safety device Effect of safety device � Evaluation method � Evaluation method � Experimental approach (case by case: bottom up) � Experimental approach (case by case: bottom up) - e.g. driving simulator base e.g. driving simulator base - � Theoretical � Theoretical approach approach (general purpose: top down) (general purpose: top down) - e.g. concept base e.g. concept base - Dangerous relation Driver action No accident D D A A Warning Accident ： How does it change ? ： DANGER Message How does it change ? Message A A 15
Topics Topics � Theoretical � Theoretical Approach: Cognitive Driver Model Approach: Cognitive Driver Model � Concept: risk homeostasis hypothesis � Concept: risk homeostasis hypothesis � Our proposed model: � Our proposed model: maximum acceptable risk model maximum acceptable risk model 16
Risk Homeostasis Theory Risk Homeostasis Theory � Outline of the risk homeostasis theory � Outline of the risk homeostasis theory � A driver behaves based on a target level of risk � A driver behaves based on a target level of risk � An accident rate fluctuates around a stable mean � An accident rate fluctuates around a stable mean => Risk Homeostasis Wild, G. J. S: Target Risk , PDE Publications, 1994 17
Task Model (Target Risk Model) Task Model (Target Risk Model) � A driver behaves based on a target level of risk � A driver behaves based on a target level of risk Comparator, Summing Point Target Decisions Taken + Level of Risk - Actions upon Perceived Information Intake Vehicle Controls Level of Risk Conditions Vehicle Response Time Lagged Feedback Reference: Wild, G. J. S, The theory of Risk Homeostasis: Implications for Safety and Health , Risk Analysis, 1982 18
Risk Homeostasis Model Risk Homeostasis Model � An accident rate fluctuates around a stable mean � An accident rate fluctuates around a stable mean c Estimates of Protection Effect a - Desired Target Adjustment: + Level of Risk | a-b-c| ≈ 0 - b Adjustment Perceived STOP STOP Action Level of Risk Protection Features Resulting => Before ≈ After Time Lagged Feedback Accident Loss 19
Accident Rate Accident Rate Adjustment Action Adjustment Action Adjustment Action Individual Target Adjustment Action Level of Risk Individual Perceived Level of Risk Accident Rate Accident Rate Accident Rate A stable mean value Time 20
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