WREX2016 Conference Presentation - FRSI Searle Presentation, 2009 IPTM Special Problems Conference Orlando, Florida – April 20 to 24, 2009 59 ... WREX 2016 Pedestrian Conference

WREX 2016 Pedestrian Conference Presentation

May 2 - 6, 2016

By Mike W. Reade, CD 1

WREX 2016World Reconstruction Exposition

“The Effects of Carry Distance, Takeoff Angles, FrictionValues and Horizontal Speed Loss Upon First GroundContact on Pedestrian (Cyclist) Crashes”

Orlando, FloridaMay 2 - 6, 2016

Presented by:

Mike W. ReadeGraphic by: Virtual CRASH

Backgrounds (Mike W. Reade, CD)

◦ 1974 –2000

◦ Adjunct Instructor – 1993 to Present

◦ Pedestrian Training, Testing & Research 2000 to Present

◦ Consulting – 2000 to Present

2


May 2 - 6, 2016


Presentation Content

Typical pedestrian (cyclist) crash phases. Effects of pedestrian carry distance. Effects of pedestrian takeoff angles. Effects of pedestrian friction values. Effects of horizontal speed loss upon

ground impact.

3

Presentation Content

Effects of vertical height differences between takeoff & landing.

Pedestrian drop testing. Discuss the effects of roadway slope. Head contact/impact speed estimates. Discuss the overall effects when

considering all factors.

4


May 2 - 6, 2016


A Typical Pedestrian Crash[1] (Video)

Crash Test 1 = 21.5 mph (34.6 kph) Crash Test 2 = 22.5 mph (36.3 kph)

5

A Typical Pedestrian Crash[2]

Pre-CrashPhase

ImpactPhase

CarryDistancePhase

AirbornePhase

HorizontalSpeed Loss

Phase

PedestrianSlidingPhase

6


May 2 - 6, 2016


Pre-Crash Phase/Analysis

Slide to stop method in cases where vehicle is braking before impact.

Results can be combined with the pedestrian projectile analysis.

V 2 gd

7

Pre-Crash Phase/Analysis

Any pre-braking is combined with pedestrian projectile analysis.

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May 2 - 6, 2016


Impact Phase

First contact with pedestrian.

9Virtual CRASH Graphic (www.vcrashusa.com)

Pedestrian Trajectories (Top View)


Forward Projection Trajectory

Wrap Trajectory

Vehicle Speed = 30 mph (48 km/h) Searle Min = 78.9 % of Vehicle Speed

Throw D: 51.31 ft/15.63 m)

Throw D: 39.89 ft (12.15 m)Searle Min: 23.6 mph (38.1 km/h)


May 2 - 6, 2016


Pedestrian Trajectories (Prospective View)


Vehicle Speed = 30 mph (48 km/h)

IPTM Controlled Tests[3, 8]



May 2 - 6, 2016


Combined Speed Analysis

Combined Speed Method:

Where:◦ V1 = Pre-Crash Speed Loss◦ V2 = Pedestrian Projectile Results

2 2C 1 2V V V

13

Projectile Throw Analysis

Searle Minimum Formula[4, 5, 6]:◦ Validated for many years though testing.◦ Can be adjusted to suit various situations.

Results underestimate vehicle’s speed.

◦ Pedestrian acquires < 100% of vehicle’s speed unless a forward projection trajectory.

min 22 gSV1

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May 2 - 6, 2016


Projectile Throw Analysis

min 22 gSV1

Where:

µ = Ped friction valueg = Gravitational accelerationS = Total throw distance

µ

S

15

Pedestrian Throw Analysis

Example: [Throw D (S) = 100ft (30.48m), µ = 0.66]

min 22 gSV1

min 22 0.66 32.2 100V

1 0.66

minV 54.41 fps 37.1mph

min 22 gSV1

min 22 0.66 9.81 30.48V

1 0.66

minV 16.58 m / s 59.69 kph

Imperial: Metric:

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May 2 - 6, 2016


Carry Distance Phase (0:00 sec)


What is the pedestrian’s carry distance?




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Head Tracking (0:30 sec)



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Carry Distance Phase[1]

29

Carry Distance Phase (1/30 frames)

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Carry Distance Analysis[6]

min 2

2 g dSV

1

µ

Where:

µ = Ped friction valueg = Gravitational accelerations = Total throw distanced = Carry distance

d

S

Reference: Searle Presentation, 2009 IPTM Special Problems ConferenceOrlando, Florida – April 20 to 24, 2009 59

Carry Distance Analysis

Searle research[6]:

◦ 2.62 ft (0.8 m)

Becker/Reade research[1]:

◦ Data from 126 wrap tests.◦ 3.90 ft (1.19 m) – [s.d. 1.63 ft (0.50 m)]

Usually the carry distance is unknown. Throw D (S) is reduced by Carry D (d).

min 2

2 g dSV

1

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May 2 - 6, 2016


Airborne Phase (0:25 sec)

Starts after separating from the vehicle.





May 2 - 6, 2016







May 2 - 6, 2016


Airborne Analysis

Could use the airborne formula, if…◦ Vertical height (h) is known. Use “-” h for landing

higher than takeoff.◦ Takeoff angle (θ) is measured counter clockwise.◦ Horizontal distance (D) is between separation

and first touchdown on road.

2.73 DSCos h D Tan

“Fundamentals of Traffic Crash Reconstruction” Vol. 2 of the Traffic Crash Reconstruction Series Daily * Shigemura * Daily © 2006, ISBN 978-1-884566-63-9

7.96 DS

Cos h D Tan

Imperial: Metric:

65

Airborne AnalysisWhere:

D= Horizontal distanceθ = Takeoff angleh = Lands lower

D hθ

2.73 DSCos h D Tan

“Fundamentals of Traffic Crash Reconstruction” Vol. 2 of the Traffic Crash Reconstruction SeriesDaily * Shigemura * Daily © 2006, ISBN 978-1-884566-63-9

Imperial: Metric:

7.96 DS

Cos h D Tan

66


May 2 - 6, 2016


Airborne Analysis

?

Since it is difficult in most cases to determine where the pedestrian first touches down on the road surface, this method is normally not used.

The other challenge is deciding upon what takeoff angle to use.

θ = ?

67

θ = ?

Airborne Analysis

Pedestrian Takeoff Angles[1]:◦ Becker/Reade research[1] based upon 126 wrap

crash tests and increasing as more tests are entered.

Mean takeoff θ: 6.3 deg (s.d. 3.3 deg)

Wrap Tests

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May 2 - 6, 2016


Airborne Analysis

cSwing Golf Software. ($149 US)

All Tests Bike Tests

69

Airborne Analysis

µ

Where:

µ = Ped friction valueg = Gravitational accelerationS = Total throw distanceθ = Takeoff angle

S

2 gSV

Cos Sin

θ

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May 2 - 6, 2016


Horizontal Speed Loss Phase

Pedestrian Crash Testing[1,9]

71

Crash test data:Mean: 6.53 mph / 10.5 km/hs.d. 1.11 mph / 1.78 km/h

Projectile vs. Sliding Analysis[1, 7, 9]

µ

Where:

µ = Ped friction valueg = Gravitational accelerationS = Total throw distanced = Ped sliding distance

S

min 22 gSV1

vs:

d

V 2 gd

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May 2 - 6, 2016


Projectile vs. Slide Speed Analysis

Here, the pedestrian’s slide to stop results are less than the Searle Minimum results.

Reason?◦ Due to a horizontal speed loss upon pedestrian

ground impact.

min 22 gSV1

vs: V 2 gd

73

Horizontal Speed Loss Analysis

Horizontal Speed Loss on Ground Impact:◦ Becker/Reade research[1] based upon 126 wrap


Mean: 6.53 mph (10.51 km/h)

s.d. 1.06 mph (1.70 km/h)

HorizontalSpeed Loss ?

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May 2 - 6, 2016



θ

H

ov v sin

2V v 2gH

v

µ

Where:

vo = Original takeoff velocityv = Vertical velocity on takeoffθ = Takeoff angle (degrees)µ = Ped friction valueg = Gravitational accelerationH = Height of C/M

75


θ

Where:

vo = 44 fps (30 mph)v = Vertical velocity on takeoffθ = 10 degreesµ = 0.66g = 32.2 f/s/sH = 3 ft

H

v 44 0.1736 7.64 fps

2V 0.66 7.64 2 32.2 3 10.46 fps 7.14mph

v

µ

V = 10.46 fps

Example:

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May 2 - 6, 2016


Pedestrian Sliding Phase

Pedestrian Sliding Analysis[1, 7, 9]

77

Pedestrian Sliding Analysis

µ

Where:

µ = Ped friction valueg = Gravitational accelerationd = Ped sliding distance

d

V 2 gd

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May 2 - 6, 2016


Pedestrian Sliding Analysis

If you are able to establish the pedestrian’s first touchdown as ground contact starts, then your results will underestimate the vehicle’s impact speed.

Because of horizontal speed loss upon ground impact.

Acquires < 100% of vehicle speed !

V 2 gd

79

Pedestrian Sliding Evidence Only? If you are only able to establish the

pedestrian’s total sliding distance, the pedestrian sliding results will underestimatethe vehicle’s impact speed.

So, determine the horizontal speed loss upon ground impact.

Add the two speed values together[1, 6, 7, 9]. The result will approximate the projectile’s

airborne speed.

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May 2 - 6, 2016


Pedestrian Friction Values[1]

81

Pedestrian Friction Values

Searle’s Sandbag Method[6]: ◦ Dry Surface: 0.715 Mean

◦ Wet Surface: 0.695 Mean

◦ Frost Surface: 0.40 Mean

◦ Overall Value: 0.695 Mean



May 2 - 6, 2016


Searle’s Sandbag Method[6]

Suggested Protocol:◦ Use sandbag with a weight of about 33 lb / 15 kg, made of

denim material.

◦ Wrap sandbag in appropriate clothing material worn by pedestrian.

◦ Weigh sandbag and attach a long line of 4 meters (13 feet).

◦ Attach to back of vehicle and “slowly” ease forward at walking pace.

◦ Perform several tests and determine average pull force.

◦ Weigh sandbag again and use mean value.

◦ Correct for slight upward pull angle as attached to vehicle.


Searle’s Sandbag Method

Reference: Searle Presentation, 2009 IPTM Special Problems ConferenceOrlando, Florida – April 20 to 24, 2009

Sandbag Tests Protocol:

◦ The resulting value incorporates the surface gradient and no further correction is required.

( )( )=

- ×

Pμ

hW P l

Where:P = Average PullW = Sandbag Weighth = Height of Attachment Pointl = Length of Rope/Wire

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May 2 - 6, 2016




Denim Sandbag Test Example:Sandbag 1st Weight: 33 lbSandbag 2nd Weight: 32 lbSandbag Mean Weight (W): 32.5 lbSandbag Pulls (P): 21, 23, 25, 22, 24 (Avg: 23)Attachment Height (h): 14 inches (1.16 feet)Rope Length (l): 12 feet (144 inches)

Determine the adjusted friction value to use for your pedestrian sliding on the surface you tested.

0.759 vs. 0.707.....( )( )=

- ×

Pμ

hW P l

85



Denim Sandbag Test Example:Sandbag 1st Weight: 33 lbSandbag 2nd Weight: 32 lbSandbag Mean Weight (W): 32.5 lbSandbag Pulls (P): 19, 20, 17, 19, 18 (Avg: 18.6)Attachment Height (h): 14 inches (1.16 feet)Rope Length (l): 12 feet (144 inches)

Determine the adjusted friction value to use for your pedestrian sliding on the surface you tested.

0.605 vs. 0.572.....( )( )=

- ×

Pμ

hW P l

86


May 2 - 6, 2016



Hill’s Asphalt Friction Values[6]:◦ Serge Jacket & Trousers: 0.702

◦ Body Warmer & Trousers: 0.723

◦ Nylon Jacket & Trousers: 0.567

◦ Woollen Boiler Suit: 0.750

◦ Rubber Jacket/Trousers: 0.735

◦ Mean Value: 0.695

◦ Std. Dev.: 0.073



Bovington Friction Results[6]: ◦ Nylon Rain Suit: 0.532

◦ Leather M/C Suit: 0.562

◦ Nylon M/C Suit: 0.608

◦ Woollen Boiler Suit: 0.633

◦ Rubber Jacket/Trousers: 0.612


◦ Std. Dev.: 0.039



May 2 - 6, 2016



Test Dummy Friction Results[1]: ◦ Albuquerque, NM Class: 0.67

◦ Fort McCoy, WI Class: 0.59

◦ Augusta, ME Class: 0.50

◦ Sewell, NJ Class: 0.54

◦ Scotch Plains, NJ Class: 0.59

◦ Narragansett, RI Class: 0.66


◦ Std. Dev.: 0.08

Reference: IPTM Test Dummy Friction TestingAs part of Pedestrian Courses 89


Winter Pedestrian Testing[9]: ◦ Wet Asphalt Surface: 0.58

◦ Snow/Slush Mixture: 0.53

◦ Packed Snow Mixture: 0.45


◦ Std. Dev.: 0.03

Reference: CATAIR Winter Pedestrian Testing ResultsRiverview, NB Canada – January 2011

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May 2 - 6, 2016


Pedestrian Friction Values Overall Mean Values: ◦ Searle’s Sandbag Method: 0.69 Mean

◦ Searle Suggested Value: 0.66 (Asphalt)

◦ Searle Suggested Value: 0.70 (Asphalt)

◦ Hill’s Friction Results: 0.69 Mean

◦ Bovington’s Friction Results: 0.58 Mean

◦ IPTM Dummy Results: 0.59 Mean

◦ IPTM Crash Tests (139 tests): 0.61 Mean

◦ CATAIR Winter Testing: 0.52 Mean


◦ Std. Dev.: 0.0691

Pedestrian Slide to Stop Results

Example: (Slide D = 65 ft (19.81 m), µ = Ped Values)◦ Searle Sandbag Tests (0.69): 36.6 mph (59.0 km/h)

◦ Hill’s Friction Results (0.69): 36.6 mph (59.0 km/h)

◦ Bovington’s Results (0.58): 33.6 mph (55.1 km/h)

◦ Searle’s Suggested µ (0.66): 35.8 mph (57.7 km/h)

◦ IPTM Ped Classes (0.59): 33.9 mph (54.6 km/h)

◦ IPTM Crash Testing (0.61): 34.4 mph (55.4 km/h)

◦ CATAIR Winter Tests (0.52): 31.8 mph (51.2 km/h)

(Overall Mean “ µ ” Value of All Results: 0.63)

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May 2 - 6, 2016


Projection Efficiency[1, 4, 5, 6, 7, 9]

Pedestrian Speed Acquired From Vehicle:◦ Becker/Reade research[1] based upon 126 wrap


Mean Vehicle %: 87 % Searle(1983) %: 77.5 %

Wrap Tests

(Vehicle Impact Speed vs. Searle Min Results) 93

Pedestrian Crash Test Data

µ = 0.66

S = 56 ft

min 22 gSV 27.76 mph1

d = 21 ft

SLIDEV 2 gd 20.39 mph

Impact: 35.29 mph

35.2927.76% 78.6 %

35.2920. 5 739 %% 7.

(Horizontal Speed Loss: ?)

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May 2 - 6, 2016


Both results underestimate the vehicle’s impact speed because:◦ Searle Min Speed vs. Vehicle Speed. (78.6 %)

◦ Ped Slide Speed vs. Searle Min Speed. (73.4 %)

◦ Ped Slide Speed vs. Vehicle Speed. (57.7 %)

Pedestrian Crash Test Data

Impact: 35.29 mph Sliding: 20.39 mph

95

Special Considerations

Change in vertical height between takeoff and touchdown[1, 5, 6].

Roadway slope[5, 6]. Vehicle & pedestrian weights[5, 6].

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May 2 - 6, 2016


Effects of Vertical Height Change[5]

S

H

2

H2 g SV

1

µ

Where:

µ = Ped friction valueS = Total throw distanceg = Gravitational accelerationH = Height of C/M

97

Effects of Vertical Height Change

H = 25 ft

2

H2 g SV

1

Where:

µ = 0.66S = 100 ftg = 32.2 f/s/sH = 25 ft

3ftV 53.86 fps 36.7mph

25ftV 49.71fps 33.8mph

No HV 54.41fps 37.1mph

θ

θ

98


May 2 - 6, 2016


Effects of Roadway Slope[5] (Downhill)

S

α

2

1Cos2 g SV

n

1

Si

µ

Where:

µ = Ped friction valueα = Roadway slope (degrees)S = Total throw distanceg = Gravitational acceleration

Degrees = Tan-1 Slope (%)

99

Effects of Roadway Slope[5] (Uphill)

S

α

2

1Cos2 g SV

n

1

Si

µ

Where:

µ = Ped friction valueα = Roadway slope (degrees)S = Total throw distanceg = Gravitational acceleration

Degrees = Tan-1 Slope (%)

100


May 2 - 6, 2016


Effects of Roadway Slope

No Slope: 37.1 mph (59.7 km/h) Uphill results: 38.5 mph (61.9 km/h) Downhill results: 35.5 mph (57.1 km/h)

2

1Cos2 g SV

n

1

Si

Where:

µ = 0.66α = ± 3 degreesS = 100 ft (30.48 m)g = 32.2 fps2 (9.81 m/s2)

[Difference: +1.4 mph (+2.2 km/h) & -1.6 mph (-2.6 km/h)]

101

Effects of Veh & Ped Weight[6]

No Weights: 37.1 mph (59.7 km/h) One Pedestrian: 38.6 mph (62.1 km/h) Two Pedestrians: 40.4 mph (65 km/h)

2M m s

1M2 gV

Where:

µ = 0.66M = 4200 lb (1909 kg)m = 175 lb (79.5 kg)s = 100 ft (30.48 m)g = 32.2 fps2 (9.81 m/s2)

(Two Peds)m = 175 lb (79.5 kg)m = 200 lb 90.9 kg)

[Difference: +3.3 mph (+5.3 km/h)]102


May 2 - 6, 2016


Effects of All Considerations [6]

Searle Minimum : 37.1 mph (59.7 km/h)

Carry Distance: 36.3 mph (58.5 km/h)

Weight: 38.6 mph (62.2 km/h)

Height, Weight: 38.2 mph (61.5 km/h)

Height, Weight, Slope: 37.2 mph (59.9 km/h)

All Considerations: 36.4 mph (58.6 km/h)

[Difference: +1.5 mph (+2.5 km/h) to – 0.7 mph (-1.2 km/h)]

2

1M

2 g SV

1

Cos Sim

d

M

n H

Where:

µ = 0.66M = 4200 lb (1909 kg)m = 175 lb (79.5 kg)α = - 2 degreesS = 100 ft (30.48 m)d = 4 ft (1.22 m)H = 3 ft (0.91 m)g = 32.2 fps2 (9.81 m/s2)

103

Controlled Crash Test Data[1]

Let us consider the following situation: Impact Speed (Vericom): 28.17 mph (45.32 km/h) Pedestrian Throw D: 44.33 ft (13.51 m) Pedestrian Airborne D: 25.53 ft (7.78 m) Pedestrian Sliding D: 18.8 ft (5.73 m) Pedestrian Friction Value: 0.66 Pedestrian Carry D: 2.62 ft (0.80 m) Pedestrian Takeoff θ: 8 degrees

How much of a difference does it make?

104


May 2 - 6, 2016


Controlled Crash Test Data[1, 11]

◦ Searle Min Only: 24.7 mph (39.7 km/h) (87%)

◦ Searle Min @ Takeoff θ: 27.35 mph (44 km/h) (97%)

◦ Searle Min @ Carry: 23.96 mph (38.55 km/h)(85%)

◦ Searle Min @ H (3.33 ft): 24.08 mph (38.74 km/h)(85%)

◦ Searle Min @ H (10 ft): 22.79 mph (36.67 km/h)(81%)

◦ Searle Min @ - 2o Slope: 24.03 mph (38.66 km/h)(85%)

◦ Searle Min @ +2o Slope: 25.3 mph (40.27 km/h) (89%)

◦ Searle Min @ Weights: 25.0 mph (40.22 km/h) (88%)

◦ Searle Min @ All (- 2o): 22.96 mph (36.94 km/h)(81%)

◦ Searle Min @ All (+ 2o): 24.20 mph (38.93 km/h)(85%)

◦ Searle Min Mean Value: 24.43 mph (39.32 km/h)(86%)

105

Controlled Crash Test Data◦ Pedestrian Sliding Analysis: Pedestrian Sliding D: 18.8 ft (5.73 m) Pedestrian Friction Value: 0.66 Pedestrian Sliding Result: 19.29 mph (31.03 km/h)

◦ Pedestrian Airborne Analysis: Pedestrian Horizontal D: 25.53 ft (7.78 m) Pedestrian Vertical D: 3.33 ft (1.01 m) Pedestrian Takeoff : 8 degrees Pedestrian Airborne Result: 26.76 mph (43.05 km/h)

[Difference: - 7.47 mph (12.02 km/h)]

106


May 2 - 6, 2016


Crash Result Comparisons[1, 11]

◦ Vehicle Impact Speed: 28.17 mph (45.32 km/h)

◦ Ped Sliding Speed: (93.6%) 26.37 mph (42.43 km/h) [From Sliding Distance: (68.4%) 19.29 mph (31.03 km/h)] [Horizontal Speed Loss: 7.08 mph (11.39 km/h)]

◦ Ped Airborne Speed: (94.9%) 26.76 mph (43.05 km/h)

◦ Searle Min Speed: (87.7%) 24.73 mph (39.79 km/h)

◦ Searle Min 8o Speed: (97.0%) 27.35 mph (44.28 km/h)

◦ Ped Sliding / Ped Airborne: 98.5 %

107

Quick Field Analysis[6] (Bratten: SAE 890859)

Vehicle Impact Speed: 28.17 mph (45.32 km/h)

Searle Minimum Speed: 24.7 mph (39.74 km/h)

Ped Sliding + Loss Speed: 26.37 mph (42.43 km/h)

Bratten Formula Speed: 25.76 mph (41.45 km/h)

Where:

s = 44.33 ft (13.51 m)g = 32.2 fps2 (9.81 m/s2)V = ? fps ( ? m/s)

[Bratten vs. Impact Speed: – 2.41 mph (-3.87 km/h), or 91.4%]

37.78 fps 25.76 m hV s pg

Reference: The Physics of Throw Distance in Accident ReconstructionJohn A. Searle, Road Accident Analysis Service, UK, SAE 930659

11.51m / s 41.45 k hV s pg

108


May 2 - 6, 2016


Head Strike Locations[1]

Does the vehicle’s design effect where the pedestrian’s head will impact the vehicle?

Does the pedestrian’s height effect where the head will impact on the vehicle?

Can the head strike location be used to estimate the vehicle’s impact speed?

109

Head Strike Locations

Ford Ford

25-30 mph

30-45 mph

45-60 mph60+ mph

110


May 2 - 6, 2016



1978 Oldsmobile Cutlass : Vehicle Speed = 26.35 mph 111


2002 Kia Rio : Vehicle Speed = 28.20 mph 112


May 2 - 6, 2016



1993 Ford Van : Vehicle Speed = 18.09 mph 113

Head Strike Locations[1, 8]

High Front Vehicle at 30 mph (48 km/h)


Low Front Vehicle at 30 mph (48 km/h)


May 2 - 6, 2016


Head Strike Locations[1, 8]

Vehicle at 30 mph (48 km/h)



Head strike location depends on much more than just the vehicle’s speed.

Depends upon vehicle design, hood length, pedestrian height, hood height, etc.

So, speed alone is not the deciding factor of where a pedestrian’s head will first impact on the vehicle.

116


May 2 - 6, 2016


Drop Test Research Experiments

Pedestrian Drop Testing Data[1, 9]

117

Drop test data:Mean: 7.08 mph / 11.39 km/hs.d. 0.78 mph / 1.26 km/h

Drop/Fall Data

d = ?

A pedestrian drops, or falls off the back of a moving vehicle.

You do not know the vehicle’s speed, you only know the pedestrian’s sliding distance.

What can we do?

S = ?

118

H = ?


May 2 - 6, 2016


Drop/Fall Data

d = 28.28 ft

Determine the pedestrian’s sliding distance. Determine the pedestrian’s friction value. Using , find the pedestrian’s sliding

speed for that phase of the event.

S = ?

μ = 0.58

V 2 gd

119

Drop/Fall Data

Vslide = 32.5 fps (22.16 mph)

The resulting speed provides for the pedestrian sliding phase only.

Determine the height from which the pedestrian fell, or is dropped.

S = ?

H = ?

120


May 2 - 6, 2016


Drop/Fall Data

Determine the vertical velocity (Vy) of the pedestrian upon striking on the road surface.

Then, let us determine the amount of horizontal speed loss ( Vloss) upon ground impact.

S = ?

H = 5.25 ft

2 2y oV v sin 2 g H

loss yV V

Vy = 18.387 fps

= 10.66 fps (7.27 mph)

121

Drop/Fall Data


This is what we know so far. Let’s determine the pedestrian drop/fall

time using:

S = ?

H = 5.25 ft t = ?dslide = 28.28 ft

Vloss = 10.66 fps (7.27 mph)

2Htg

μ = 0.58

122


May 2 - 6, 2016


Drop/Fall Data


The drop/fall time is used to determine the horizontal airborne distance.

But, what horizontal velocity is used to determine the distance?

S = ?

H = 5.25 ft t = 0.571 secdslide = 28.28 ft

Vloss = 10.66 fps (7.27 mph)μ = 0.58dairborne = ?

123

Drop/Fall Data


Add Vslide and Vloss , then use the resulting total as your horizontal velocity to calculate horizontal airborne distance.

S = ?

H = 5.25 ft t = 0.571 sec

dslide = 28.28 ftVloss = 10.66 fps (7.27 mph)

μ = 0.58dairborne = Vx ∙ t

Vx = 43.16 fps (29.43 mph)

124


May 2 - 6, 2016


Drop/Fall Scenario


The resulting pedestrian speed is 29.43 mph at the start of drop/fall.

The total travel distance then becomes 52.92 ft.

S = 29.43 mph (43.16 fps)

H = 5.25 ft t = 0.571 sec

dslide = 28.28 ftVloss = 10.66 fps (7.27 mph)

μ = 0.58dairborne = 24.64 ft

dtotal = 52.92 ft

125

Drop/Fall Data Comparison[9]

Ped Slide Speed = 22.18 mph

Vert. Velocity/Landing = 18.38 fps

Horz. Speed Loss = 7.27 mph

Total Fall Time = 0.571 sec

Airborne Dist. = 24.64 ft

Start of Fall Speed = 29.43 mph

S = 31.7 mph

Ped Slide Speed = 22.18 mph

Horz. Speed Loss = 7.27 mph

Airborne Dist. = 26.55 ft

Radar Speed = 31.7 mph

From “Three” field measurements: μ = 0.58

dslide = 28.28 ftH

“Calculated From Test Data” “Determined From Test Data”

“Results are: -2.27 mph, or 92.8 % of Test Speed” 126


May 2 - 6, 2016


127

128

y = 0.8541xR² = 0.6454

0.000

10.000

20.000

30.000

40.000

50.000

60.000

0.00 10.00 20.00 30.00 40.00 50.00 60.00

Sea

rle

Min

imu

m S

pee

d (

MP

H)

Test Speed (MPH)

Searle Minimum Equation V. Test SpeedWraps

Searle Min Formula = Impact Speed Linear (Searle Min)


May 2 - 6, 2016


Searle Minimum (Wraps)

n=126 Most of the time results are under

predicted on average by 85% Also speaks to projection efficiency Predicts Speed ± 10.93 mph with 95%

confidence

129

130

y = 1.0096xR² = 0.4921

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00

Sea

rle

Max

imu

m S

pee

d (

MP

H)

Test Speed (MPH)

Searle Maximum Equation V. Test SpeedWraps

Searle Max Formula = Test Speed Linear (Searle Max) Linear (Formula = Test Speed)


May 2 - 6, 2016


Searle Max (Wraps)

n=126 Many times will over predict the vehicle’s

speed Projection Efficiency on average 101% Predicts Speed ± 13.25 mph with 95%

confidence

131

132

y = 0.9015xR² = 0.7782

0.000

5.000

10.000

15.000

20.000

25.000

30.000

35.000

40.000

45.000

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00

Sea

rle

Min

imu

m S

pee

d (

MP

H)

Test Speed (MPH)

Searle Minimum V. Test SpeedForward Projection

Searle Minimum Searle Minimum = Test Speed Linear (Searle Minimum)


May 2 - 6, 2016


Searle Min - Forward Projection

n=8 Tendency to under predict Projection Efficiency on average 90% Predicts Speed ± 15.53 mph with 95%

confidence More tests required

133

134

y = 1.0192xR² = 0.7707

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00

Sp

eed

Max

imu

m S

pee

d (

MP

H)

Test Speed (MPH)

Searle Maximum Speed V. Test SpeedForward Projection

Searle Maximum Searle Maximum = Test Speed Linear (Searle Maximum) Linear (Searle Maximum = Test Speed)


May 2 - 6, 2016


Searle Max - Forward Projection

n=8 Can over predict by 1% Projection Efficiency on average 101% Predicts Speed ± 17.73 mph with 95%

confidence More tests required

135

136


May 2 - 6, 2016


137

6.33

3.32

126

x

s

n

138

6.53

1.06

126

x

s

n


May 2 - 6, 2016


139

5.20

1.11

8

x

s

n

Statistical Conclusions

Wraps:◦ Searle Min most of the time under estimated

and gave 85% of the vehicle speed on average.◦ Searle Max may over estimate or under

estimate.(S ± 13.25 mph at 95% conf.)

140


May 2 - 6, 2016



Forward Projections:◦ Searle Min most of the time under estimated.

(S ± 15.53 mph at 95% conf.)◦ Searle Max may over estimate or under

estimate.(S ± 17.73 mph at 95% conf.)

141


Friction Values for Asphalt:◦ Uniform distribution◦ Average 0.61◦ (S ± 0.18 at 95% conf.)

142


May 2 - 6, 2016



Horizontal Speed Loss (Wraps):◦ Normal distribution◦ Average 6.53 mph◦ (S ± 2.12 mph at 95% conf.)

143


Horizontal Speed Loss (Forward Proj.):◦ Normal distribution◦ Average 5.20 mph◦ (S ± 2.22 mph at 95% conf.)

144


May 2 - 6, 2016



Pedestrian Slide vs. Searle Min:

◦ Pedestrian slide underestimates vehicle speed all the time.◦ On average gave 61% of the vehicle speed.◦ (S ± 13% at 95% conf.)

22 gSV 2 gd vs. V1

145

Crash Test Statistics

146


May 2 - 6, 2016


Sources1. Becker, T.L., Reade, M.W. (2008 to 2016) “Analysis of Controlled

Pedestrian/Cyclist Crash Testing Data.” IPTM-UNF Pedestrian/Bicycle Crash Investigation Courses.

2. Reade, M.W. (2011) “The Anatomy and Analysis of a Typical Pedestrian/Bicycle Crash Event.” Proceedings of the NATARI Annual Combined Conference, Harrisburg, Penn.

3. Becker, T., Reade, M., Scurlock, B. (2015) “Simulations of Pedestrian Impact Collisions with Virtual CRASH 3 and Comparisons with IPTM Staged Tests.” Cornell University Library, arXiv: 1512.00790.

4. Searle, J.A., Searle, A. (1983) “The Trajectories of Pedestrians, Motorcycles, Motorcyclists, etc., Following a Road Accident.” SAE Technical # 831622.

5. Searle, J.A. (1993) “The Physics of Throw Distance in Accident Reconstruction.” SAE Technical # 9306759.

147

Sources6. Searle, J.A. (2009) “The Application of Throw Distance Formulae.” IPTM

Special Problems in Traffic Crash Reconstruction, Orlando, Florida.

7. Hague, D.J. (2001) “Calculation of Impact Speed from Pedestrian Slide Distance.” Metropolitan Laboratory Forensic Science Service, ITAI Conference.

8. Virtual CRASH 3 (2016) “Software for Accident Reconstruction.” Web Site: http://www.vcrashusa.com/ , North America and Caribbean Distributor, Newberry, Florida.

9. Reade, M.W. (2011) “CATAIR Atlantic Region Pedestrian Crash, Drop & Friction Testing.” Riverview, New Brunswick, Canada.

10. Sullenberger, G.A. (2014) “Pedestrian Impact on Low Friction Surface.”SAE Technical # 2014-01-0470.

11. PEDBIKE 2000 Plus “Pedestrian and Bicycle Speciality Software.” Web Site: http://www.frsi.ca/, Riverview, New Brunswick, Canada.

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May 2 - 6, 2016


Conference Paper

149

New IPTM Book

150


May 2 - 6, 2016


Conference Materials

151

The materials related to this presentation may be downloaded from the following web site.

http://www.frsi.ca/ ◦ Go to: (WREX2016 Page)

◦ Conference Paper

◦ Presentation PowerPoint (PDF)

◦ Presentation Videos

◦ Some Source Papers

Summary

There are several effects that need be considered in your analysis.

Knowing how they effect your final results is important.

Thank you.

152

Graphic by: Virtual CRASH

Documents

WREX2016 Conference Presentation - FRSI Searle Presentation, 2009 IPTM Special Problems Conference Orlando, Florida – April 20 to 24, 2009 59 ... WREX 2016 Pedestrian Conference