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Effect of Driver Response on Vehicle Control Loss during a Rear Tire Tread Separation Wilson Consulting, LLC.

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Presentation on theme: "Effect of Driver Response on Vehicle Control Loss during a Rear Tire Tread Separation Wilson Consulting, LLC."— Presentation transcript:

1 Effect of Driver Response on Vehicle Control Loss during a Rear Tire Tread Separation Wilson Consulting, LLC

2 Q: What is the principal issue?A: Injuries Q: How do the injuries occur?A: Rollovers, 3/30 Rule Q: How do the rollovers occur?A: Loss of Control Q: How does loss of control occur? A: Drift Off Road/Missed Curve (39%) Tread Separation (25%) Accident Avoidance(18%) Other (17%) Wilson Consulting, LLC Problem Statement

3 Wilson Consulting, LLC Overview Examples of Real-World Tread Separation Accidents Examples of Real-World Tread Separation Accidents Factors Affecting Loss of Control Factors Affecting Loss of Control Human Factors Considerations Human Factors Considerations

4 Examples of Real-World Tread Separation Events Wilson Consulting, LLC

5 Partial Tread Separation/Air Out Partial Tread Separation/Air Out Carcass Blow Out Tread Partially Attached

6 Accident Scene Evidence Partial Tread Separation/Air Out Left Front Left Rear Tire/Rim Skips

7 Accident Scene Evidence Rim Gouge & Tire Marks – Tread Separation/Air Out Left Front Left Rear

8 Accident Scene Evidence Rim Gouge &Tire Marks – Tread Separation/Air Out Accident Scene Evidence Rim Gouge &Tire Marks – Tread Separation/Air Out Right Front Right Rear Left Rear

9 Accident Scene Evidence Start of Pre-Roll Yaw Marks – Tread Separation Accident Scene Evidence Start of Pre-Roll Yaw Marks – Tread Separation

10 Accident Scene Evidence Pre-Roll Yaw Marks – Tread Sep Accident Scene Evidence Pre-Roll Yaw Marks – Tread Sep Left Rear Right Rear Left Front Right Front

11 Accident Scene Evidence End of Tire Marks – Tread Sep Accident Scene Evidence End of Tire Marks – Tread Sep Left Front Left Rear

12 Factors Affecting Loss of Control During Tread Separation Vehicle CharacteristicsVehicle Characteristics Vehicle SpeedVehicle Speed Driver ResponseDriver Response Driver ExpectancyDriver Expectancy Prior Experience with Tread SeparationsPrior Experience with Tread Separations Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

13 Factors Affecting Loss of Control During Tread Separation Vehicle CharacteristicsVehicle Characteristics Vehicle SpeedVehicle Speed Driver ResponseDriver Response Driver ExpectancyDriver Expectancy Prior Experience with Tread SeparationsPrior Experience with Tread Separations Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

14 Circle Test at Low Speed Ackerman Steer Angle Ackerman Low Speed Low Speed Minimal Lateral Acceleration Minimal Lateral Acceleration No Tire Scrub No Tire Scrub Ackerman Steer Angle is the Amount of Steer Required To Drive The Vehicle in the Prescribed Circular Path (usually 100 ft radius) Circular Path

15 At-Limit Understeer Increased Speed Requires Increased Steer to Maintain Prescribed Circular Path Ackerman Steer Increased Speed Increased Speed Increased Steer Increased Steer Increased Lateral Acceleration Increased Lateral Acceleration Understeer Gradient = Additional Steer/Increase in Lateral Acceleration Understeer Gradient = Additional Steer/Increase in Lateral Acceleration Additional Steer Ackerman Steer Additional Steer

16 Effect of Understeer Gradient on Loss of Control Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Drivers Are More Likely to Maintain Control in a Vehicle with High Understeer Gradient Wilson Consulting, LLC

17 Vehicle Understeer Gradient Vehicle’s Understeer Gradient and Inherent Directional Stability Are Drastically Reduced by a Rear Tire Tread Separation Baseline Understeer Gradient (deg/g) Understeer Gradient w/ Tread Sep (deg/g) Change in Understeer Gradient Comments 4.81.1-3.7NADS, upper limit generic SUV 4.5Less than 0.0More than -4.5Dickerson, Bronco II 3.50.1-3.4NADS, middle value generic SUV 2.4-1.2-3.6NADS, lower limit generic SUV

18 Other Vehicle Characteristics that Adversely Affect Loss of Control * Effect Caused by Passenger and Cargo Loading Move CG Rearward* Move CG Rearward* o Reduces Understeer Lateral Load Transfer* Lateral Load Transfer* o Reduces Understeer Increase CG Height* Increase CG Height* o Reduces Rollover Stability o Increases Lateral Load Transfer Low Roll Stiffness Low Roll Stiffness o Reduces Effective Trackwidth o Increases Lateral Load Transfer Front-to-Rear Roll Stiffness Ratio Front-to-Rear Roll Stiffness Ratio o Reduces Understeer

19 Factors Affecting Loss of Control During Tread Separation Vehicle CharacteristicsVehicle Characteristics Vehicle SpeedVehicle Speed Driver ResponseDriver Response Driver ExpectancyDriver Expectancy Prior Experience with Tread SeparationsPrior Experience with Tread Separations Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

20 Effect of Vehicle Speed on Loss of Control Drivers More Likely to Experience Loss of Control at Higher SpeedsDrivers More Likely to Experience Loss of Control at Higher Speeds In NHTSA Study, Speeds Ranged from 71-81 mph at Time of Tread SeparationIn NHTSA Study, Speeds Ranged from 71-81 mph at Time of Tread Separation Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

21 Factors Affecting Loss of Control During Tread Separation Vehicle CharacteristicsVehicle Characteristics Vehicle SpeedVehicle Speed Driver ResponseDriver Response Driver ExpectancyDriver Expectancy Prior Experience with Tread SeparationsPrior Experience with Tread Separations Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

22 Initial Driver Response to Tread Separation (Vehicles 1-3) Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Driver Responses with Experimenter Interaction Not Included Steering Was Initial Reaction for Drivers Who Were Not Expecting Tread Separation Initial Response of Drivers Steering or Braking Wilson Consulting, LLC

23 Effect of Driver Expectancy on Loss of Control Ability to Maintain Control of Vehicle Strongly Associated with Expectancy Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Percentage of Drivers that Experienced Vehicle Loss of Control Wilson Consulting, LLC Vehicle 1

24 Effect of Driver Expectancy on Loss of Control Ability to Maintain Control of Vehicle Strongly Associated with Expectancy Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Percentage of Drivers that Experienced Vehicle Loss of Control Wilson Consulting, LLC Vehicle 2

25 Effect of Driver Expectancy on Loss of Control Ability to Maintain Control of Vehicle Strongly Associated with Expectancy Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Percentage of Drivers that Experienced Vehicle Loss of Control Wilson Consulting, LLC Vehicle 3

26 Initial Driver Response to Tread Separation (Vehicles 1-3) Expectancy/Experience Improved Likelihood of Maintaining Control Whether Initial Response was Steering or BrakingExpectancy/Experience Improved Likelihood of Maintaining Control Whether Initial Response was Steering or Braking Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Driver Responses with Experimenter Interaction Not Included Wilson Consulting, LLC

27 Factors Having Minimal Effect on Loss of Control During Tread Separation Written Instructions on Maintaining Vehicle Control During a Tread SeparationWritten Instructions on Maintaining Vehicle Control During a Tread Separation Driver AgeDriver Age Right vs. Left Tread SeparationRight vs. Left Tread Separation Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

28 Human Factors that Affect Driver’s Ability to Maintain Vehicle Control During a Tread Separation Event Wilson Consulting, LLC ExpectancyExpectancy Prior Tread Separation ExperiencePrior Tread Separation Experience Perception-Response TimePerception-Response Time

29 Comparison of “Tread Separation” Tests Comparison of Actual Tread Separation Test to a Single-Wheel Braking TestComparison of Actual Tread Separation Test to a Single-Wheel Braking Test Single-Wheel Braking Test Simulates Vehicle Motion (Yaw and Yaw Rate) Caused by Tread Separation EventSingle-Wheel Braking Test Simulates Vehicle Motion (Yaw and Yaw Rate) Caused by Tread Separation Event Source: SAE Paper 2007-1-0836, Tandy, Carr, Liebbe, et al. Wilson Consulting, LLC

30

31 Test Driver Response to Actual Tread Separation Test Test Driver Expecting Tread Separation and Subsequent Clockwise RotationTest Driver Expecting Tread Separation and Subsequent Clockwise Rotation Test Driver’s Stimulus for Initial Reaction (Steer Left) is Noise/Vibration Caused by Tread Separation, not Vehicle’s Clockwise MotionTest Driver’s Stimulus for Initial Reaction (Steer Left) is Noise/Vibration Caused by Tread Separation, not Vehicle’s Clockwise Motion Test Driver Steers Left Simultaneously as Vehicle Starts to Rotate ClockwiseTest Driver Steers Left Simultaneously as Vehicle Starts to Rotate Clockwise Wilson Consulting, LLC

32 Perception-Response Process 1.Detection – Sensory Stimulus that Allows Driver to Become Aware of a Potential Hazard 2.Identification – Driver Must Acquire Sufficient Information to Decide What Response, If Any, is Appropriate 3.Decision – Typically, Driver Decision is to Change Direction, Change Speed or Both 4.Response – Driver’s Brain Issues Instructions to Appropriate Muscle Groups to Carry Out Intended Action Olson, Farber, Forensic Aspects of Driver Perception and Response, Second Edition, 2003

33 Test Driver’s Perception-Response Process 1.Detection – Driver Perceives Tread Separation by Noise and Vibration Caused by Tread-to-Vehicle Interaction 2.Identification – Test Driver Need Not Identify Perceived Hazard Because Driver is Expecting Tread Separation 3.Decision – Test Driver Response Already Pre- Determined Because Driver is Expecting Tread Separation and Driver Has Experience Handling Tread Separations 4.Response – Movement of Steering Wheel By Driver Wilson Consulting, LLC

34 Test Driver’s Perception-Response Process 1.Detection – Driver Perceives Tread Separation by Noise and Vibration Caused by Tread-to-Vehicle Interaction 2. 3. 4.Response – Movement of Steering Wheel By Driver Wilson Consulting, LLC Expectation of Tread Separation and Prior Experience with Tread Separations Eliminates Step 2 (Identification) and Step 3 (Decision) from P-R Process

35 Test Driver Response to Actual Tread Separation Test Test Driver’s Response Time is Unrealistically ShortTest Driver’s Response Time is Unrealistically Short (0.4 sec) When Compared to Response Times in Real- World, Unexpected Tread Separations (0.4 sec) When Compared to Response Times in Real- World, Unexpected Tread Separations Test Driver’s Amount of Steer is Inconsistent with Typical Emergency Steer Inputs (Test Driver Experienced with Tread Separations)Test Driver’s Amount of Steer is Inconsistent with Typical Emergency Steer Inputs (Test Driver Experienced with Tread Separations) Even with Unrealistically Fast Response Time, Vehicle Still Diverts Entirely From Original Lane of Travel and Never Returns to Original Lane of TravelEven with Unrealistically Fast Response Time, Vehicle Still Diverts Entirely From Original Lane of Travel and Never Returns to Original Lane of Travel Wilson Consulting, LLC

36 Driver’s Perception-Response Process in Real-World Tread Separation Event (Part 1) 1)Detection – Driver Detects Tread Separation by Noise and Vibration Caused by Tread-to-Vehicle Interaction 2)Identification – Most Drivers Unable to Identify that Tread is Separating from Rear Tire Based on Noise/Vibration Unable to Proceed to Step 3 (Decision) Because Perceived Hazard Not Identified Unable to Proceed to Step 3 (Decision) Because Perceived Hazard Not Identified Wilson Consulting, LLC

37 Driver’s Perception-Response Process in Real-World Tread Separation Event (Part 2, P-R Start Over) 3)Detection – Driver Perceives Unexpected Change in Vehicle Heading 4)Identification – Without Driver Input, Vehicle Will Exit Roadway 5)Decision – Steer To Avoid Leaving Roadway 6)Response – Movement of Steering Wheel by Driver Wilson Consulting, LLC

38 Driver Response Time to Single-Wheel Braking Test Similar to Real-World Driver Response Driver’s Response Time is 1.2 to 1.5 Seconds After Start of Vehicle’s Clockwise RotationDriver’s Response Time is 1.2 to 1.5 Seconds After Start of Vehicle’s Clockwise Rotation Driver’s Response Time is 1.6 to 1.9 Seconds After Start of Noise/Vibration from Tread SeparationDriver’s Response Time is 1.6 to 1.9 Seconds After Start of Noise/Vibration from Tread Separation In Real–World, Unexpected Tread Separation Events, Drivers Steer in Response to the Vehicle’s Unexpected Change in Heading Caused by Tread SeparationIn Real–World, Unexpected Tread Separation Events, Drivers Steer in Response to the Vehicle’s Unexpected Change in Heading Caused by Tread Separation Wilson Consulting, LLC

39 Effect of Driver Response Time on Vehicle Loss of Control * Achieved Loss of Control ** Emergency Steer Inputs * Achieved Loss of Control ** Emergency Steer Inputs Tread Separation TestSingle-Wheel Braking Test Max Yaw Caused by Tread Sep 8 deg (CW)More Than 25 deg (CW) Max Yaw Rate Caused by Tread Sep 15 deg/s (CW)*35 deg/s (CW)* Max Lateral Acceleration Caused by Tread Sep 0.4 g1.0 g Response Time (Vehicle Starts to Yaw) 0.0 sec1.2-1.5 sec Steer60 deg – L 90 deg - R 280 deg – L** 50 deg - R Initial Steer Rate50 deg/s550 deg/s**

40 Braking Wilson Consulting, LLC

41 Effect of Initial Driver Response to Tread Separation on Loss of Control (Vehicles 1–3) Drivers More Likely to Maintain Control if Braking was Initial Response Drivers More Likely to Maintain Control if Braking was Initial Response Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” in the National Advanced Driving Simulator (NADS)” Driver Responses with Experimenter Interaction Not Included Wilson Consulting, LLC

42 NHTSA Study Demonstrates Favorable Results if Braking is Initial Response to Tread Separation Event However, When conducting test of 15-passenger vans subject to rear tire tread separation/air-outs, “STL and Michelin determined that braking after the blow out would be dangerous, and the [professional] driver stated that he would be uncomfortable conducting the test if he were required to brake.” (NTSB /HAR-03/03, PB2003-916203, July 15, 2003) Wilson Consulting, LLC

43 Conclusions

44 1)Vehicle Can Experience Loss of Control Solely as a Consequence of Tread Separation. 2)Driver’s Initial Response Was to Steer in Unexpected Tread Separation Events. 3)Driver Expectancy Strongly Affects Ability to Maintain Control. 4)Driver Expectancy Significantly Reduces Perception-Response Time. Wilson Consulting, LLC

45 1)Vehicle Can Experience Loss of Control Solely as a Consequence of Tread Separation. 2)Driver’s Initial Response Was to Steer in Unexpected Tread Separation Events. 3)Driver Expectancy Strongly Affects Ability to Maintain Control. 4)Driver Expectancy Significantly Reduces Perception-Response Time. Wilson Consulting, LLC

46 1)Vehicle Can Experience Loss of Control Solely as a Consequence of Tread Separation. 2)Driver’s Initial Response Was to Steer in Unexpected Tread Separation Events. 3)Driver Expectancy Strongly Affects Ability to Maintain Control. 4)Driver Expectancy Significantly Reduces Perception-Response Time. Wilson Consulting, LLC

47 1)Vehicle Can Experience Loss of Control Solely as a Consequence of Tread Separation. 2)Driver’s Initial Response Was to Steer in Unexpected Tread Separation Events. 3)Driver Expectancy Strongly Affects Ability to Maintain Control. 4)Driver Expectancy Significantly Reduces Perception-Response Time. Wilson Consulting, LLC

48 5)Vehicle’s Rotation and Yaw Rate Increase as Driver’s Response Time Increases. 6)Response of Professional Drivers in Expected Tread Separation Tests Do Not Accurately Reflect Reponses of Drivers in Unexpected Real-World Tread Separation Events. 7)Drivers with Prior Tread Separation Experience Can Anticipate Vehicle’s Motion Thereby Minimizing Vehicle’s Yaw and Yaw Rate.

49 5)Vehicle’s Rotation and Yaw Rate Increase as Driver’s Response Time Increases. 6)Response of Professional Drivers in Expected Tread Separation Tests Do Not Accurately Reflect Reponses of Drivers in Unexpected Real-World Tread Separation Events. 7)Drivers with Prior Tread Separation Experience Can Anticipate Vehicle’s Motion Thereby Minimizing Vehicle’s Yaw and Yaw Rate.

50 5)Vehicle’s Rotation and Yaw Rate Increase as Driver’s Response Time Increases. 6)Response of Professional Drivers in Expected Tread Separation Tests Do Not Accurately Reflect Reponses of Drivers in Unexpected Real-World Tread Separation Events. 7)Drivers with Prior Tread Separation Experience Can Anticipate Vehicle’s Motion Thereby Minimizing Vehicle’s Yaw and Yaw Rate.

51 8)Given Normal Driver Response Times in Real- World Tread Separations, Emergency Steer or “Abrupt” Maneuvers Are Necessary When Attempting to Control Vehicle. 9)Written Instructions on Maintaining Vehicle Control During a Tread Separation Have Minimal Effect on Loss of Control.

52 8)Given Normal Driver Response Times in Real- World Tread Separations, Emergency Steer or “Abrupt” Maneuvers Are Necessary When Attempting to Control Vehicle. 9)Written Instructions on Maintaining Vehicle Control During a Tread Separation Have Minimal Effect on Loss of Control.

53 Thank you for your attention. Lawrence A. Wilson, P.E. Wilson Consulting, LLC wilsonconsulting@verizon.net


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