Pedestrian Collisions

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Winifred Blake
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1 Pedestrian Collisions

2 Your case is only as good as your investigation. At trial, the attack is on the evidence, not the calculations.

3 July 28, :05 AM John I have a hit and run. I have not been able to establish the area of contact. The accident scene was not secured, the victim's body was removed prior to my arrival. The prosecutor would like to know if you might be available to do a reconstruction. Thanks, Marvin

4 AN EXTRAORDINARY PIECE OF INVESTIGATION

5 900 ft before the AOI

6 1000 ft before the AOI

7 Remember: The defense often focuses on events/behavior before the AOI (causation).

9 RECONSTRUCTION ISSUES: WHERE DID THE IMPACT HAPPEN? POI or AOI HOW DID THE PEDESTRIAN GET THERE? WHAT WAS THE VEHICLE SPEED? WAS THE COLLISION AVOIDABLE?

11 The POI is where the hat is.

13 The impact may lift the pedestrian out of their shoes. CSI

14 PEDESTRIAN STRUCK FROM REAR

15 4 ms LATER

16 or the shoes may be thrown forward by contact with the vehicle NY v. Joe Gray

17 NY v. Joe Gray SHOES POI

18 Garmin Forerunner 210 sport watch 180 hr memory USB connect to computer

19 Path of pedestrian

20 HOW DID THE PEDESTRIAN GET THERE? EYE WITNESSES PATH OF PEDESTRIAN PARKED VEHICLES??? PEDESTRIAN INJURIES WALKING SPEED OF PEDESTRIAN

21 Include parked vehicle(s) in drawing

22 HOW DID THE PED GET THERE? Pedestrian walking parallel to path of car, or pedestrian stationary when struck

23 In line damages

24 HOW DID THE PED GET THERE? Pedestrian crossing the path of the car

27 WHAT DIRECTION WAS PED WALKING? ROSA CINTRON NY v. Joe Gray POI WITNESS SAYS

28 WHAT DIRECTION WAS PED WALKING? DEFENDANT SAYS NY v. Joe Gray POI

29 NY v. Joe Gray

30 scrapes on bumper

31 scrapes on bumper

32 The medical examiner or forensic pathologist may be a valuable witness.

33 HOW DID THE PEDESTRIAN GET THERE: THE AUTOPSY

34 ROAD CONTACT VEHICLE CONTACT CSI

35 How much time did it take for the pedestrian to reach the AOI? ( pedestrian walking speed )

36 Walking speeds (ft/sec) for 30 yr old males: LOW HIGH (10 TH %ile) (90 TH %ile) Hermance Thompson Eubanks Boise State U San Diego

37 AN AVERAGE VALUE IS JUST ABOUT USELESS!

38 Walking speeds (ft/sec) for 30 yr old males: LOW HIGH Hermance Thompson Eubanks Boise State U San Diego

39 ALWAYS USE A RANGE of values

40 Impact Configuration d S w

41 Impact Configuration d t = d / 1.47 S w S w

42 Backing the Car to Prior Point d S c d = 1.47 S c t

43 WHAT WAS THE VEHICLE SPEED? TIRE MARK EVIDENCE INJURIES ( forensic pathologist ) THROW OF PEDESTRIAN BODY HEAD STRIKE ON VEHICLE??? EVENT DATA RECORDER ( black box )

44 SKID MARKS ( LOCKED WHEEL BRAKING )

45 skid patch on tire

46 CSI Light-to-dark

47 shadow

48 FAUX DEFENSE: TIRE MARK RESIDUE WAS NOT MATCHED TO TIRES ON DEF s VEHICLE

49 HIT-RUN PEDESTRIAN CRASH Sample #1 from tire mark residue Sample #2 from tire of def s car

50 But some chemical tests are too sensitive, and detect contamination.

51 COMPARISON:

52 Defense expert s I was able to demonstrate that the skid marks were made by different tires (not the defendant s).

53 Response to defense expert s are you aware of any research/testing/papers, etc. where remnants of ground rubber were obtained from the road surface

54 Defense expert s I don t know of any reference materials regarding that testing. I just made it up as I went along, like I do with everything else.

55 ABS scuff marks

56 CSI SPECKLING on tire

57 ABS SCUFF MARKS

58 MINIMUM SPEED FROM SKID : S 30 fd 30 = constant w/unit conversions f = drag factor d = skid distance η = brake percentage (brake efficiency)

59 MINIMUM SPEED FROM SKID : S 30 fd WHY IS IT A MINIMUM SPEED ESTIMATE?

60 shadow brakes applied

61 As much as 30% of the kinetic energy can be lost before visible skid marks. Reed and Keskin, SAE # Overgaard et al, SAE CSI

62 vehicle may not have stopped at the end of the skid

63 SOME AUTHORS DEFINE AN EFFECTIVE DRAG FACTOR f eff = f η

64 MINIMUM SPEED FROM SKID : S 30 fd S 30 fd f and η are combined into one number

65 MINIMUM SPEED FROM SKID : S 30 fd

66 d = 172 ft S 30 fd f = 0.72 η = 1.0

67 S 30 fd

68 S 30 fd S 30(.72)(172)(1.0) S S 60.9 mph

69 S 30 fd S 30(.72)(172)(1.0) S S 60.9 mph

70 How to avoid an attack on uncertainties in the data: Calculate a RANGE of speeds instead of a single minimum speed.

71 Skid Speed nomograph:

72 When testifying, less math is the best math, because

73 JURORS DON T LIKE MATH!

74 Keep the numbers to a minimum! JUROR

75 Estimated speed from skid : RF = 118 ft η = 0.30 LF = 117 ft η = 0.30 RR = 111 ft η = 0.20 LR = 114 ft η = 0.20 d = ft used in calculation f = 0.80, f = 0.78, f = 0.79, f = 0.80 f avg = used in calculation S = 30 f d η = mph

76 BAD! JUROR

77 JUROR GOOD!

78 Rule 705. Disclosing the Facts or Data Underlying an Expert Unless the court orders otherwise, an expert may state an opinion and give the reasons for it without first testifying to the underlying facts or data.

79 HOW IS SKID DISTANCE DETERMINED? d

80 SKID MARKS ALWAYS* DIFFER IN LENGTH

81 IT WOULD BE UNUSUAL TO FIND ALL FOUR SKID MARKS EQUAL IN LENGTH.

82 HOW DO WE DETERMINE SKID DISTANCE FROM FOUR TIRE MARKS?

84 Determining skid distance, d : Simple average model Weight shift model Center of mass motion (longest skid)

85 Determining speed from skid marks : Simple average 48.3mph model 48.6 mph Weight shift model Center of mass motion 48.9 mph 52.3 mph

86 What is drag factor? Drag factor is an index that designates how sticky, or frictional, the road is DRAG FACTOR = FRICTION FORCE WEIGHT CAUSING FRICTION

87 WHAT CAUSES FRICTION? ROAD SURFACE

88 WHAT CAUSES FRICTION? ROAD SURFACE A road, itself, does not have a unique drag factor value

89 WHAT CAUSES FRICTION? TIRE ROAD SURFACE

90 DOES f DEPEND ON THE TIRES? + drag factor - motorcycle tires performance tires domestic car tires commercial truck tires

91 DRAG FACTOR DOES NOT DEPEND ON TIRE PRESSURE on a dry road Over a range of 5 60 psi there was less than 5% variation in drag factor in tests with bias ply, radial, and recapped tires. Jan/Feb, 1993 Acc Reconstruction Journal SAE# Reduced pressure did not affect drag factor

92 WHAT CAUSES FRICTION? CONDITIONS TIRE ROAD SURFACE

93 WHAT CAUSES FRICTION? VEHICLE BRAKING SYSTEM TIRE ROAD SURFACE

94 Drag factor for ABS vehicles is slightly higher than non-abs on dry surfaces. Drag factor for ABS vehicles is significantly higher than non- ABS on wet surfaces.

95 HOW CAN A TIRE THAT IS ROLLING PRODUCE A MARK? HOW CAN A TIRE THAT IS NOT LOCKED PRODUCE MORE FRICTION THAN A SKIDDING TIRE?

96 FRICTION CONVENTIONAL BRAKES TIME

97 100% WHEEL LOCKUP

98 ANTILOCK BRAKES TIME

99 ABS provides an average improvement in drag factor of 13.6%. Bartlett and Jobe, Dry Pavement Stops with and without ABS: New Vericom Data, Accident Reconstruction Journal, March/April 2013

100 TYPICAL f VALUES DRY ASPHALT WET ASPHALT ( ACTUAL VALUES MAY LIE OUTSIDE THESE RANGES )

101 HOW IS DRAG FACTOR MEASURED? f

102 Measuring Friction with a Drag Sled CSI

103

104

105 ACCELEROMETER

106 DISPLAY MOTION SENSOR SAMPLING PRINTOUT

107

108 Vbox Sport racelogic.com

109 ACTUAL OR EXEMPLAR VEHICLE USED FOR TEST ACCELEROMETER MOUNTED TO VEHICLE ACCELEROMETER LEVELED 100% BRAKING APPLIED TO VEHICLE DRAG FACTOR DATA DOWNLOADED

110 Side-by-side comparison of drag sled and accelerometer Wakefield, et al. NATARI Newsletter, 1995

111 Regional Crash Investigation Team, November, 2009 Roanoke County, VA #1 #2 #3 #4 #5 VC drag sled ipod app Regional Crash Investigation Team, November, 2009 Roanoke County, VA

112 Masory and Wright, Error Analysis for Three Different Methods of Determining Drag Factor, tarorigin.com

113 A properly designed, properly pulled, and "tuned" drag sled can yield values for Average Drag Factor that converge quite well with the VC-2000 values. Understanding The Vericom VC-2000 Accelerometer- Pitfalls for the Operator, Ed Livesay, tarorigin.com

114 HOW IS BRAKE PERCENTAGE DETERMINED? η

115 BRAKE PERCENTAGE % of vehicle weight that is causing friction INOPERATIVE BRAKES MOTORCYCLE TRACTOR TRAILER

116 20% 30% 20% 30% typical weight distribution

117 20% 30% 20% INOPERATIVE ( 0% braking ) η = 70% =.70

118 THROW OF THE PEDESTRIAN S BODY Basic theory: The faster the striking vehicle speed, the farther the body will be thrown.

119

120 THROTHTH POI THROW DISTANCE FRP

121 V = 2 f g d cos Θ + ( f sin Θ) Θ =? GENERAL FORM OF THE SEARLE EQUATION, 1983

122 THE GENERAL FORM OF THE SEARLE EQUATION CAN BE SOLVED FOR A MINIMUM SPEED MAXIMUM SPEED

123 V min = 2 f g d 1 + f 2 V max = 2 f g d

124 V min = 2 f g d 1 + f 2 V max = 2 f g d

125 drag factor values from literature: Stcherbatcheff (combined air/ground) Collins.80 Searle Limpert Eubanks, p Becke Schneider Severy IPTM chart IPTM, people tumbling 1.0 Eubanks, personal communication

126 The speed is for the pedestrian s body, not the vehicle. SAE #

127

128 Searle Speed nomograph: Speed of pedestrian body

129 CRASH TESTS:

130 Searle maximum speed Searle minimum speed

131 Searle maximum speed vehicle speed, 1993 Searle minimum speed

132 A NIGHT UNDER THE EL People v. Joe Gray

133

134 Speed from throw distance: (without the math) Appel Searle Sterbatchoff Wood Bratten Limpert 55.0 mph 54.2 mph 49.2 mph 53.8 mph 51.3 mph 54.2 mph

135 Speed from throw distance: (without the math) Appel Searle Sterbatchoff Wood Bratten Limpert 55.0 mph 54.2 mph 49.2 mph 53.8 mph 51.3 mph 54.2 mph As if this weren t bad enough

136 NY v. Joe Gray Gray stated that he braked just before hitting the pedestrians, but he was too close to them to stop.

137 Speed from throw distance: (without the math) Appel Searle Sterbatchoff Wood Bratten Limpert 55.0 mph 54.2 mph 49.2 mph 53.8 mph 51.3 mph 54.2 mph Speed from braking distance 52.4 mph

138 RESULT ONE: DEFENSE EXPERT DID NOT TESTIFY RESULT TWO: CONVICTION

139 Just trying to get the driver s speed down a little.

140 Not a forward projection.

141 EVENT DATA RECORDER (EDR)

142 Can the EDR store data in a pedestrian strike?

143 vehicle behavior speed EDR ΔV operator behavior braking steering

144 Blackthorn GPS forensics tool

145 GPS GLOBAL POSITIONING SYSTEM LOJACK OnStar Smart phone Garmin GPS Fit watch school buses fleet trucks

146 Garmin portable GPS 24 hours of data speed every second downloadable with Cellebrite

147 VIDEO CAMERAS store cameras traffic monitors parking lots municipal buildings parking garages CSI

148 TRAFFIC CAMERA

149 WAS THE COLLISION AVOIDABLE?

150 Beware of the human factors expert!

151 visualexpert.com

152 HUMAN FACTORS: perception-reaction time pedestrian walking speed use a RANGE of values

153 Where does the analysis of avoidance start? Point of first possible perception

154 What is the point of first possible perception?

155 It is the vehicle location WHEN THE DANGER PRESENTS.

156 Beware of the one size fits all number!

157 VIDEOTAPED VISIBILITY TEST

158 IN-CAR VIDEO

159

160 -2.0 sec

161 -0.6 sec

162 0.0 sec

163 Do not be bullied out of your common sense by the expert. Oliver Wendell Holmes, Jr.

164 PEOPLE OF NY v. BOZICK What might happen when a prosecutor has the courage to file a motion to exclude a defense expert s testimony.

165 Under the conditions of this accident, at night, with an unexpected pedestrian on a dark rural road, perception is not likely to occur prior to impact.

166 the operator s first perception would either be with the feel or the sound of the impact.

167 If a driver s eye position were in this position, objects 150 ft away on the roadway edge would be 5 o from central vision (in the peripheral field of vision).

168 Moon illumination at 80% of a full moon would have provided less than.002 footcandles (Liebowitz, 1987) which would be insufficient for detection of a pedestrian.

169 The People submit that the fact that he struck a person with his vehicle is not an element of the crime. Why he struck a person is not an element of the crime.

170 The People submit that this testimony is not relevant to the elements of the crime charged and is intended to simply confuse the legal issue for the jury.

171 A well crafted motion to exclude convinced the judge it was

172 Following a review of all the submitted material, I find that the proferred testimony of Dr. Kennedy relates to an issue that is NOT beyond the ken of the average juror. Therefore, there is no need to permit testimony of an expert such as Dr. Kennedy as proposed by the defendant.

173 PHASES IN IMPACT AVOIDANCE d r REACTION d a AVOIDANCE

174 The PRT process (and impairment)

175 The PRT process (and impairment)

176 There is no such thing as the human perception-reaction time. Dr. Marc Green visualexpert.com PRT is a statistical concept!

177

178 1.5 seconds... is a good upper bound estimate, meaning that a substantial percentage (i.e. 85% to 95%) of reasonably alert drivers will respond within 1.5 seconds. Paul L. Olson

179 2.5 seconds... large enough to include the time taken by nearly all (90% of all) drivers under most highway conditions. AASHTO Policy on Design Standards for Highways

180 What is a reasonable RANGE of PRT values?

181 The probable range of perceptionresponse times for reasonably straightforward situations should be 0.75 to about 1.5 seconds. Paul L. Olson, Forensic Aspects of Driver Perception and Response, 1996, p. 187

182 Location Day Night Straight s s Intersection s s & curves Table 14-4 Chapter 14 of the Handbook for Human Factors in Litigation, Muttart, 2004.

183 What is a reasonable RANGE of PRT values for an impaired operator?

184 WAS THE COLLISION AVOIDABLE? COULD THE COLLISION BE AVOIDED BY A SOBER DRIVER OPERATING AT THE POSTED SPEED?

185 reaction distance: the distance the vehicle moves during the operator s PRT d = 1.47 S t

186 S 30 fd speed from skid marks braking distance d S 30 2 f

187 braking distance: the distance it takes for the brakes to stop the vehicle d r d d b S 2 30 f

188 TOTAL STOPPING DISTANCE d r d d s = 1.47St + + S 30 2 f d b

189 TOTAL STOPPING DISTANCE S = 30 mph PRT = 1.5 sec d r d b d s = = 106 ft

190 TOTAL STOPPING DISTANCE S = 50 mph PRT = 3.0 sec d r d b d s = = 243 ft

191 TOTAL STOPPING DISTANCE 30 mph, sober 106 ft 50 mph, impaired 243 ft

192 turn away (swerve) distance: the distance it takes for the vehicle to steer away from the pedestrian d r d TA d TA = S L / f

193 TOTAL TURN AWAY DISTANCE d r d b d TA = 1.47St S L / f

194 TOTAL TURN AWAY DISTANCE S = 30 mph PRT = 1.5 sec L = 1 ft d r d b d TA = = 79 ft

195 TOTAL TURN AWAY DISTANCE S = 50 mph PRT = 3.0 sec L = 1 ft d r d b d TA = = 153 ft

196 TOTAL TURN AWAY DISTANCE 30 mph, sober 79 ft 50 mph, impaired 153 ft

Single Vehicle Loss of Control

. Single Vehicle Loss of Control the natural motion is to continue in the same direction weight shifts to outside of turn INERTIA weight shifts to outside of turn INERTIA friction a yaw occurs when the