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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 Problem Statement 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

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

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

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

6 Accident Scene Evidence Partial Tread Separation/Air Out
Left Rear Left Front 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
Right Front Left Rear Right Rear

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

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

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

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

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

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

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

16 Effect of Understeer Gradient on Loss of Control
Drivers Are More Likely to Maintain Control in a Vehicle with High Understeer Gradient Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” 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 4.8 1.1 -3.7 NADS, upper limit generic SUV 4.5 Less than 0.0 More than -4.5 Dickerson, Bronco II 3.5 0.1 -3.4 NADS, middle value generic SUV 2.4 -1.2 -3.6 NADS, lower limit generic SUV

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

19 Factors Affecting Loss of Control During Tread Separation
Vehicle Characteristics Vehicle Speed Driver Response Driver Expectancy Prior Experience with Tread Separations Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios 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 Speeds In NHTSA Study, Speeds Ranged from mph at Time of Tread Separation Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios in the National Advanced Driving Simulator (NADS)” Wilson Consulting, LLC

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

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

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

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

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

26 Initial Driver Response to Tread Separation (Vehicles 1-3)
Expectancy/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)” Driver Responses with Experimenter Interaction Not Included Wilson Consulting, LLC

27 Right vs. Left Tread Separation
Factors Having Minimal Effect on Loss of Control During Tread Separation Written Instructions on Maintaining Vehicle Control During a Tread Separation Driver Age Right vs. Left Tread Separation Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios 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 Expectancy Prior Tread Separation Experience Perception-Response Time Wilson Consulting, LLC

29 Comparison of “Tread Separation” Tests
Comparison 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 Event Source: SAE Paper , Tandy, Carr, Liebbe, et al. Wilson Consulting, LLC

30 Wilson Consulting, LLC

31 Test Driver Response to Actual Tread Separation Test
Test 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 Motion Test Driver Steers Left Simultaneously as Vehicle Starts to Rotate Clockwise Wilson Consulting, LLC

32 Perception-Response Process
Detection – Sensory Stimulus that Allows Driver to Become Aware of a Potential Hazard Identification – Driver Must Acquire Sufficient Information to Decide What Response, If Any, is Appropriate Decision – Typically, Driver Decision is to Change Direction, Change Speed or Both 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
Detection – Driver Perceives Tread Separation by Noise and Vibration Caused by Tread-to-Vehicle Interaction Identification – Test Driver Need Not Identify Perceived Hazard Because Driver is Expecting Tread Separation Decision – Test Driver Response Already Pre-Determined Because Driver is Expecting Tread Separation and Driver Has Experience Handling Tread Separations Response – Movement of Steering Wheel By Driver Wilson Consulting, LLC

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

35 Test Driver Response to Actual Tread Separation Test
Test Driver’s Response Time is Unrealistically Short (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) Even 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)
Detection – Driver Detects Tread Separation by Noise and Vibration Caused by Tread-to-Vehicle Interaction 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 Wilson Consulting, LLC

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

39 Effect of Driver Response Time on Vehicle Loss of Control
Tread Separation Test Single-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 g 1.0 g Response Time (Vehicle Starts to Yaw) 0.0 sec sec Steer 60 deg – L 90 deg - R 280 deg – L** 50 deg - R Initial Steer Rate 50 deg/s 550 deg/s** * Achieved Loss of Control ** Emergency Steer Inputs

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 Source: NHTSA Report “Investigation of Driver Reactions to Tread Separation Scenarios 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, PB , July 15, 2003) Wilson Consulting, LLC

43 Conclusions Wilson Consulting, LLC

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

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

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

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

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

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

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

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

52 Given Normal Driver Response Times in Real- World Tread Separations, Emergency Steer or “Abrupt” Maneuvers Are Necessary When Attempting to Control Vehicle. 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


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