1. Human Factors For Traffic Crash Reconstruction Is it Avoidable? INTRODUCTION (c) J. Muttart 2009

2. Why Reconstruct a Crash? Is it avoidable! Why Reconstruct a Crash? Is it avoidable! Human Factors in a Crash Speed choice Deceleration choice Search time Start up time (from green light to rolling wheels) Acceleration rate Detection probability Response time Response choice (decision making) Walking speed Situational awareness Information Processing Fatigue, age, alcohol, environment, cell use, work zones, vision… (c) J. Muttart 2009

3. Elements REQUIRED for Avoidance Opinion ① How much time did the driver have available ② What is the average response time for THAT scenario ③ ③ What was the speed of the vehicle ④ ④ Given the time left (1 minus 2) and the speed (3) – can the driver steer or slow enough to clear the impact area without contact. (c) J. Muttart 2009

4. ① Time Available How long was the other object or vehicle Easily identifiable As an immediate hazard That required an emergency response i.e.- How long before impact was A dark pedestrian at night 1 st discernable? A stopped vehicle on a highway 1 st noticeable as traveling very slow? An intruding vehicle 1 st discernable as entering the intersection The lead vehicle’s taillights illuminated (if the responder is following close behind – not approaching)? Crossing into the path of the responder? (c) J. Muttart 2009

5. Factors that Influence Conspicuity CLiPSCONTRAST Does the object differ from the background? LIGHTING Is the object illuminated above threshold (you cannot see white objects in a closed closet) PATTERN Can the shape of the object be recognized (camouflage works!) SIZE (c) J. Muttart 2009

6. Pattern: Visible Vs. Discernable (c) J. Muttart 2009

7. Contrast

8. LIGHTING Example Case: Pedestrian Crossing R to L at 6.6 ft/sec (2 m/s) – travels 19.7 feet (6 m) at 90 degrees relative to vehicle Driver traveling 40 mph (58.7 ft/s - 64.4 km/h – 17.9 m/s) “Never saw him” – 9006 Headlight “Never saw him” – 9006 Headlight Pedestrian strike right of center on car When does pedestrian enter headlight beam? (c) J. Muttart 2009

9. Pedestrian Enters Beam at ~ 150 feet from Impact Car moved 58.7’ For every 6.6’ (c) J. Muttart 2009

10. Kn Sound Kn Light Path Intrs TraffSgnl Peds/Bikes

11. Question! Why would we need to know the acceleration rate of a vehicle? Time of the Intruder to get to impact… or Time available for the responder (c) J. Muttart 2009

12. Easily Identifiable Path Intrusions How long did it take intruder to accelerate from the stop line (turning location) to impact? Drivers start slow, vehicle rolls while foot moves to throttle Then normal acceleration Then acceleration decreases until traveling desired constant speed (c) J. Muttart 2009

13. Is AR Using Appropriate Acceleration? Things to consider 4-way stop intersection (slowest) 2-way stop intersection (faster) Arterial exit (Tim’s) (fastest) Approaching traffic (faster) Stop to 1 st lane (slowest) Longer acceleration at large intersection (medium) From stop line (neglecting slow start up) to 2 nd lane or start of 3 rd (fastest) IF YOU DO NOT KNOW TIME AVAILABLE HOW CAN YOU SAY IT IS AVOIDABLE OR UNAVOIDABLE? (c) J. Muttart 2009

14. Pass. Car 40 ft (12.2 m) Accelerations Four Way Stop / Traffic Signal From stop ~0.14 1 st sec~0.06 (Fugger et al) From stop line~0.23 – 0.27 Two Way Stop - Light Traffic From stop ~0.16 1 st Sec~0.08 ( Kodsi et al.) From stop line~0.26 Stop at Heavier traffic (fast food restaurant) From stop ~0.19 From stop line~0.29 (Muttart; Craig) (c) J. Muttart 2009

15. Phase III Phase II Phase I Acceleration is a behavior! Green line = Average acceleration Velocity (c) J. Muttart 2009 Typical Acceleration Profile

16. Response Time For THAT event How much of available time is necessary to respond? (c) J. Muttart 2009

17. Definition CANNOT APPLY PRT UNTIL DISCERNABLE [CLiPS] PERCEPTION Of an IMMEDIATE hazard that requires an IMMEDIATE response RESPONSE The action taken by the driver Open Loop Time (approximately ½ sec) Leg movement (braking) Hand movement (steering) Closed Loop Time (approximately ¼ sec) Vehicle latency – the time necessary for full steering or full braking and the delay by the vehicle (c) J. Muttart 2009

18. Components of a Driver’s Response (c) J. Muttart 2009 Perception-Response Time |----------------Recognition Distance------------------| (Distance to Impact)

19. What number should we use? What has not worked well; 1.6 or 1.5 seconds plus or minus ½ sec 0.75 to 1.5 sec I have a (dissimilar) study that says… A book/ article says average PRT is… (for what type response?) What does work I have a similar study and I made adjustments to account for how it is different than my crash scenario I have a similar study and we can see when comparing the methodology of that case and my crash that response time would be (higher/lower) than that reported by the study. I am relying upon a systematic analysis that reports how more than 10,000 have responded and that study corroborates methods that have been utilized in reaction time research for over 140 years. (c) J. Muttart 2009

20. The Hipp Chronoscope World’s First Stop Watch Invented to measure how RT changes Reaction Time Museum – Montclair University (c) J. Muttart 2009

21. The Subtractive Method Frans Cornelius Donders (1868) On the speed of mental processes. [Translated by Kosters in Attention and Performance II, 1969] Assumes pure insertion. Task A = Task B + additional task RT A – RT B = RT additional task (c) J. Muttart 2009

22. Donders Subtractive Method (c) J. Muttart 2009

23. With a 98 mph fastball ~150 ms to decide if & how he wants to swing – Has seen pitch 250 ms. Batter knows; approximate location ~17 inch area the stimulus and the appropriate response conditioned responses Well-lighted location Misses more than 30% of the time. (c) J. Muttart 2009

24. Now lets change: Professional batter with the “average” person. Appropriate response unknown. Only one ball per 6,000 trips At night? Coming from our peripheral vision? More than one “pitcher” Also have to drive a car and hit the ball. Will we respond in the same time??? How much longer??? (c) J. Muttart 2009

25. All Responses from 155 studies More response to light studies than more complex scenarios Known Audible Or Known lights Turns, long Headways, eccentricities Mid Block Intrusion Intersection Intrusion

26. Subtractive Method Applied to Path Intrusion Studies Rice 0.64 sec Closed course to Hi Fidelity Simulator Lechner 0.80 Add Leg Movement Olson 1.08 sec Dusk Muttart 1.46 sec Night Muttart 1.58 sec On a straight Road Broen 1.33 sec Add night Muttart 1.48 sec Add Cell Task Chisholm 1.44 - 2.33 sec Low Fidelity to Closed Course Lerner 1.51 sec To Hi Fidelity Sim Muttart 1.67 sec Increased eccentricity Eubanks 1.91 sec Plus Air Brakes Shutko 1.74 sec 54.5 deg eccentricity Chang et al. 2.03 sec (c) J. Muttart 2009

28. Eccentricity Exercise: How many “stimuli” (as defined by DRIVE3) are there? Y X On calculator: Y / X Enter Shift TAN (c) J. Muttart 2009

29. Common Eccentricities Common eccentricities Speedometer/Instruments~ 16 degrees (5 to 20 degrees) Driver’s side mirror~35 degrees(25 to 40 degrees) Rear view mirror~27 degrees(20 to 35 degrees) Passenger’s side mirror~50 degrees(35 to 50 degrees) Radio/Center Console~50 degrees Left window (30 to 120 degrees) Right window (35 to 100 degrees) Car starting from a stop line to the right & in right lane (3 to 5 degrees) If eccentricity exceeds 50 degrees, enter 50. (c) J. Muttart 2009

30. No Stop Line? National Cooperative Highway Research Report 383 Harwood, Mason, Brydia, Pietrucha, & Gittings TRB 1996. Most drivers are comfortable in stopping with the front of their vehicle 6.5 ft (2 m) or less from the near edge of traveled lane. This study is cited by AASHTO Policy on Geometric Design of Highways and Streets as the basis for the intersection sight distance criteria for intersection design. (c) J. Muttart 2009

31. Using a Chart Advantages Offers a response time that corresponds to a particular scenario (rather than one-size-fits-all) Cons Like sweat pants – fits, but is clearly not the best fit or most fashionable. No information relative to “Perception threshold” (when PRT starts) See “Assumptions” (c) J. Muttart 2009

32. Solution II Obtaining an analogous study (a study in which the subject driver faced a similar response scenario) Advantages Face validity – on its face it looks better Analogous research can be used to predict average PRT (Muttart, 2004, 2005) Path intrusions predict average response time to path intrusions Responses to lead vehicles predict average response time to LVs Responses to cut-offs predict average response times to cut-offs Cons Can’t find studies No study is exactly like the case I have When different, what effect does that have (what adjustment can be used) (c) J. Muttart 2009

33. What Other Studies Say (c) J. Muttart 2009

34. Solution III Computer program Drive Cubed (Greg Russell) DRIVE3(REC-TEC) Yet unnamed program I DRIntegrated Driver Response DRMDriver Response Model Or your idea? (c) J. Muttart 2009

35. How to Use the Charts (c) J. Muttart 2009

36. Path Intrusion Example Intruder moving 20 mph – 55 feet from stop line to impact Primary driver traveling 42 ft/s (28.3 mph) (c) J. Muttart 2009

37. Eccentricity When Cleared 25 degrees (c) J. Muttart 2009

38. Path Intrusion Example Brake Lights1.45 seconds later (brake lights and steering) + 250 ms for braking latency = 1.7 sec = Actual PRT (c) J. Muttart 2009

39. Path Intrusion Example Impact Is a 1.7 sec PRT slower or faster than average for this type crash? How much slower or faster? (c) J. Muttart 2009

41. Vehicle Changing Lanes (c) J. Muttart 2009 An object that crosses into a driver’s path that was originally traveling the same direction. PRT measured 1 st lateral movement intruder 1 st Vehicle response (responder)

42. Cut-Off Example Intruder (center lane) moving from next lane Eccentricity ~ 0 deg from Responder (pickup) (Same vehicle had cut off pickup earlier) (c) J. Muttart 2009

43. Cut-Off Example Start of Response 0.57 seconds to brakes (brake lights and steering) (~0.82 to full braking) What is Average PRT & What distance is necessary to STOP? (c) J. Muttart 2009

45. Lead Vehicle Example White Van stopped on straight highway Eccentricity ~ 0 deg from Responder (pickup) Van width = 6.5 feet What is Average Response? (c) J. Muttart 2009

46. Path Intrusion Example Start of Response (above) 160 feet from impact Distance: Eye position to front of bumper = 8 ft. Approach speed = 70 mph (c) J. Muttart 2009

47. Path Intrusion Example Impact (c) J. Muttart 2009

48. Analysis of a Response to a Lead Vehicle Is there a reason for the approaching driver to know the lead vehicle was stopped? [LV stopped on a curve or at the bottom of a ramp] Yes – Go to Chart No – Calculate the visual expansion rate of the LV at which a driver would be able to recognize that they are closing dangerously fast 0.0045 to 0.006 radian/sec is most common (c) J. Muttart 2009

49. Discernability of Slow Moving Lead Vehicle Discernability Threshold ~ 320 ft Time to Contact = 320.4/102.7 = 3.12 sec (c) J. Muttart 2009

51. Modifications to Scenario What if… looking ahead & at an intersection (or cued)? or following close behind (average headway 1.5 sec) Average of all 14 real life drivers… Average PRT = 0.98 +/- 0.35 seconds (c) J. Muttart 2009

52. Practice: 85 th Percentile Response What is the response time of a driver who responds slower than 85% of all drivers for the same situation? Average PRT x 1.35 ~ 85 th percentile 1.5 x 1.35 = 2.0 sec Round to the closest 1/10 th of a second. Rounding 2.09 down to 2.0 seconds will offer a smaller range and would be inappropriate. This analysis does not have a degree of accuracy of better than 1/10 th of a second. Therefore, use of a response time of 2.26 seconds would suggest an accuracy that is not appropriate based upon the available research. (c) J. Muttart 2009

53. Thank You! (c) J. Muttart 2009