a study of pedestrian head injury evaluation method

A STUDY OF PEDESTRIAN HEAD INJURY EVALUATION METHOD

Yutaka Okamoto, Yuji Kikuchi

Honda R&D Co., Ltd. Automobile R&D Center

ABSTRACT

The EEVC WG17 Test Procedure for Head Impactor Component Test has become widely used.

However the kinematics of the whole body may influence the head injury. In this study crash tests with

the Pedestrian Dummy and with the Impactor are conducted and the main factors causing the

difference between both results are considered. Two different front shapes of vehicles, a passenger car

and a Sports Utility Vehicle (SUV), are chosen for the tests. The main factors for the differences are

the head impact velocity, three directional acceleration values for HIC and head effective mass.

Key words: PEDESTRIANS, HEAD INJURY, EVALUATION METHOD, DUMMY, EEVC

FOR THE EVALUATION of pedestrian head injuries, the impactor test proposed by the

European Enhanced Vehicle-safety Committee (EEVC) draft report [3] are mainly used and this only

takes the hood area of the vehicle into account. But from the recent pedestrian accident research it was

found that the windshield has a bigger effect on head injuries than the hood area. NHTSA conducted a

Pedestrian Injury Causation Study (PICS) from 1977 to 1980. They were interested in the influence of

the vehicle front shape of recent models, and conducted another pedestrian accident research,

Pedestrian Crash Data Study (PCDS) from 1994 to 1998 where only recent model year vehicles were

inspected. Isenberg R. [4] analyzed the data from both studies and the items found to be influenced by

the change of front shape are the vehicle - pedestrian interaction, the increase in injury because of the

windshield and A-pillar, and the decrease of thorax, abdomen and pelvis injuries. Although the head

injury cases caused by the windshield have increased in the real life pedestrian accident, it is well

known that the impactor test results against the windshield show very low HIC. And for the crash to

the SUV which has the higher hood edge, the pedestrian head velocity becomes lower than the vehicle

speed, but on the impact test the velocity is constant so it would be a more sever evaluation. In the real

life pedestrian accident, the vehicle front shape will vary the motion of the pedestrian after crash and

the head is affected by the neck and upper body. Ishikawa T. et al [5] tried to discuss this. In this study

the crash tests with the AM50 size pedestrian dummy are conducted and the main factors causing the

difference between impactor and dummy test results are considered. Two different front shapes of

vehicles, a passenger car and a SUV, are chosen for the tests. The impactor is aimed at the same

point where the dummy head contacted. The dummy head hits against the windshield of the

passenger car and against the hood of the SUV. These test results show that for the passenger car the

dummy HIC is higher than the impactor HIC and for the SUV it is opposite.

The main causes for the above results are thought as follows,

IRCOBI Conference - Madrid (Spain) - September 2006 265

1. The dummy head contact velocity is different and is dependent on the vehicle front shape

2. The dummy head has the acceleration before its contact because of the body rotation

and the accelerations of three direction occur after the contact.

3. The dummy head effective mass varies because of the external force from the neck.

Accident data analysis with recent vehicle models shows that the rate of fatal head injuries on the front

windshield and A-Pillar is higher. In this study only HIC is considered for injury criteria and some

studies say the head injury criteria should include the head rotational component, too. So the results in

this study should not be considered to explain all accident cases.

ACCIDENT DATA ANALYSYS

The trends of pedestrian accident in real life are analyzed with PICS and PCDS. The total

number of PICS is 1526 and 552 for PCDS. Figure 1 shows the trend of injury body region for AIS5+

accidents and the injury source for head injury. In PICS, not only head but also abdomen and chest are

the main region but in PCDS, head constitutes 80%. And the injury source distribution changes, too.

The rate of cowl and windshield area increases and the A-Pillar is included as well in PCDS. In PICS,

non-Contact is one of the big causes but in PCDS there are only few.

Hood Length (cm)

<50 51-75 76-100 101-125 126-150 151-175 176-2000

10

20

30

40

50

60

Ratio (%)

PICS PCDS

Carried

by Vehicle

0

10

20

30

40

50

60

Ratio (%)

PICS PCDS

Rotated over

the Vehicle

Thrown

Forward

Knocked to

Pavement

Others

Post-Crash Mode

Shunted to

Left/Right

Hood Length (cm)

<50 51-75 76-100 101-125 126-150 151-175 176-2000

10

20

30

40

50

60

Ratio (%)

PICS PCDS

Hood Length (cm)

<50 51-75 76-100 101-125 126-150 151-175 176-2000

10

20

30

40

50

60

Ratio (%)

PICS PCDSPICS PCDS

Carried

by Vehicle

0

10

20

30

40

50

60

Ratio (%)

PICS PCDS

Rotated over

the Vehicle

Thrown

Forward

Knocked to

Pavement

Others

Post-Crash Mode

Shunted to

Left/Right

Carried

by Vehicle

0

10

20

30

40

50

60

Ratio (%)

PICS PCDSPICS PCDS

Rotated over

the Vehicle

Thrown

Forward

Knocked to

Pavement

Others

Post-Crash Mode

Shunted to

Left/Right

Fig. 2 Trend of Hood Length Distribution Fig. 3 Trend of Pedestrian Mode Distribution

0

20

40

60

80

100

Ratio (%)

PICS PCDS

Head/

Face/Neck

Abdomen

Chest

AIS5+ Body Region Distribution

0

20

40

60

80

100

Ratio (%)

PICS PCDS

Non-Contact

Cowl/

WindShield

Hood

A-Pillar

Ground

Other Parts

AIS5+ Injury source of Head Injury Distribution

Bumper0

20

40

60

80

100

Ratio (%)

PICS PCDS

Head/

Face/Neck

Abdomen

Chest


0

20

40

60

80

100

Ratio (%)

PICS PCDS

Head/

Face/Neck

Abdomen

Chest


0

20

40

60

80

100

Ratio (%)

PICS PCDS

Non-Contact

Cowl/

WindShield

Hood

A-Pillar

Ground

Other Parts


Bumper0

20

40

60

80

100

Ratio (%)

PICS PCDS

Non-Contact

Cowl/

WindShield

Hood

A-Pillar

Ground

Other Parts


Bumper

Fig. 1 Trend of Body Region and Injury Source Distribution

266 IRCOBI Conference - Madrid (Spain) - September 2006

Figure 2 shows the comparison of the hood length which becomes shorter in recent vehicle

model from PCDS. Figure 3 shows the vehicle / pedestrian’s interaction and in PCDS the major mode

is “carried by vehicle”. This data shows the head mostly contacts the windshield and A-Pillar area

because of the recent front vehicle shape designs.In PICS the main mode is “knocked to pavement” or

“thrown forward” and it is considered to its square front shape. That is thought to be the one reason of

“Non-Contact” injuries. These data show that windshield and A-Pillar becomes the main injury source

for head injury because of the trend of vehicle front design.

TEST METHODS

1. PEDESTRIAN DUMMY TEST

Pedestrian Dummy (POLAR2) which was developed by Honda R&D and GESAC INC., is used

in this study. Akiyama A. et al [1] described the detail of the dummy and its biofidelity and endurance

in usage is confirmed by Kerrigan J. et al [6] and Crandall J. [2]. The dummy setting posture is shown

in Figure 4 and unifies the pre-crash dummy position. The vehicle impacts to lateral side of the

dummy that is known the most popular situation from PCDS. The Dummy is hung through an electric

magnet and released just before (0.1sec before) the vehicle hits it.

The test vehicles are of two different kinds of front shape, a passenger car and a SUV. The

dimension of them is described in Table 1. The Dummy is positioned at the vehicle center - with its

pelvis to the vehicle center line.

The vehicle velocity is 40km/h

and brakes are applied after

0.3ms of first contact with 0.5G,

so on the head contact the

vehicle speed is 40 km/h.

2. IMPACTOR TEST

The impact point is the

same place as the dummy head contact and the EuroNCAP test procedure was used. So the test

condition is Adult (4.8kg) / 40km/h / 65degree.

TEST RESULTS

1875890.4172.8SUV

1470648.7138.5Passenger Car

Bonnet End W.A.D

at Vehicle Center

(mm)

Bonnet Leading

Edge Height

(mm)

Bumper

Lead

(mm)

1875890.4172.8SUV


Bonnet End W.A.D

at Vehicle Center

(mm)

Bonnet Leading

Edge Height

(mm)

Bumper

Lead

(mm)

Table 1. Test Vehicle Dimensions

450

20

235

450

1010

1650

Target

F (mm)

D (mm)

C (mm)

A (mm)

E (mm)

B (mm)

Position

450

20

235

450

1010

1650

Target

F (mm)

D (mm)

C (mm)

A (mm)

E (mm)

B (mm)

Position

35

20

10

20

200

Target

J (deg)

I (deg)

G (mm)

K (deg)

H (deg)

Position

35

20

10

20

200

Target

J (deg)

I (deg)

G (mm)

K (deg)

H (deg)

Position

A

B

D

C

E

H I

J F

G

K

Vehicle

A

B

D

C

E

H I

J F

G

K

Vehicle

Fig. 4 Dummy Setting Posture


1. DUMMY TEST RESULT

The test results are shown in Table2. Head acceleration diagram, head velocity by film analysis

and head contact place are shown in Figure5, 6, and 7. Head accelerations, especially Gz (vertical

direction) occur at the beginning to the vehicle contact, before the head actually contacts. These

accelerations are caused by the dummy body rotation. For SUV, Gx(longitudinal direction) occurs high

because the dummy head hits from the front face. For passenger car, although the head crashes into the

windshield, HIC is over

1000.The head contact

velocity is lower than the

vehicle speed for both

vehicles and especially

SUV’s decrease is very large.

The head contact angle is

much different between them, too.

16807325.4601.4SUV

190033.433.01106.4Passenger Car

W.A.D

(mm)

Head Contact

Angle

(deg)

Head Contact

Velocity

(km/h)

HIC

16807325.4601.4SUV

190033.433.01106.4Passenger Car

W.A.D

(mm)

Head Contact

Angle

(deg)

Head Contact

Velocity

(km/h)

HIC

Table 2. Dummy Test Results

.

Y

Z

XHead Acceleration direction

(Back view)

0

20

ACC (G)

-20

40

60

80

SUV

0 50 100 150 200t(ms)

X

Y

Z

HIC=601.4

Head Contact

-20

0

20

100

ACC (G)

0 50 100 150 200

t(ms)

-40

-60

40

60

80

Passenger Car

X

Y

Z

HIC=1106.4

Head Contact

.

Y

Z


(Back view)

.

Y

Z

X ..

Y

Z


(Back view)

0

20

ACC (G)

-20

40

60

80

SUV

0 50 100 150 200t(ms)

X

Y

Z

HIC=601.4

Head Contact

0

20

ACC (G)

-20

40

60

80

SUV

0 50 100 150 200t(ms)

X

Y

Z

HIC=601.4

Head Contact

-20

0

20

100

ACC (G)

0 50 100 150 200

t(ms)

-40

-60

40

60

80

Passenger Car

X

Y

Z

HIC=1106.4

Head Contact -20

0

20

100

ACC (G)

0 50 100 150 200

t(ms)

-40

-60

40

60

80

Passenger Car

X

Y

Z

HIC=1106.4

Head Contact

Fig. 5 Head Acceleration diagrams for Dummy tests

Passenger Car SUV

T=

125

.8m

s

V=

33

.0k

m/h

T=

114

.7m

s

V=

25

.5k

m/h

:Head Contact

5

10

15

Head V(m/s)

00 50 100 150 200

t(ms)

Passenger Car SUV

T=

125

.8m

s

V=

33

.0k

m/h

T=

114

.7m

s

V=

25

.5k

m/h

:Head Contact

5

10

15

Head V(m/s)

00 50 100 150 200

t(ms)

Fig. 6 Head Velocity diagrams


2. IMPACTOR TEST RESULT

The test results are shown in Table3. The impactor acceleration diagram is shown in Figure 8.

For the passenger car, the impact point is on the windshield and the HIC is 30% of the dummy result.

This result is well known and the score of this area is recognized perfect without examination in

EuroNCAP. The front windshield consists of a laminate glass which has a laminate film between the

glasses. The first higher acceleration is caused when the glass breaks and the later low acceleration is

caused by deformation of the laminate film. There is enough clearance at this hitting point allowing for

deformation of the laminate film without any risk for impacting any underlying vehicle parts. For the SUV, the

maximum deformation is

75mm and because of the

sufficient clearance under

the hood there is no contact

with the engine parts, but

the impactor HIC is higher

than for the dummy.

DISCUSSION

The HIC in the impactor test is different from the dummy test. In the case of the contact to the

windshield for the passenger car, the impactor HIC is lower than for the dummy and to the contrary in

16806539.97931.8SUV


W.A.D

(mm)

Impact Angle

(deg)

Head Velocity

(km/h)HIC

16806539.97931.8SUV


W.A.D

(mm)

Impact Angle

(deg)

Head Velocity

(km/h)HIC

Table 3. Impactor Test Results

Passenger Car SUVPassenger Car SUV

Fig. 7 Head Contact Point

50

100

150

200

0 10 20 30 40t(ms)

ACC(G)

X

Y

Z

HIC=365.2

Passenger Car

50

-50

0

SUV

t(ms)

50

100

150

200

-50

0

ACC(G)

HIC=931.8

0 10 20 30 40 50

X

Y

Z

.ZX

Y

Impactor Acceleration direction

(Side View)

50

100

150

200

0 10 20 30 40t(ms)

ACC(G)

X

Y

Z

HIC=365.2

Passenger Car

50

-50

0

50

100

150

200

0 10 20 30 40t(ms)

ACC(G)

X

Y

Z

HIC=365.2

Passenger Car

50

-50

0

SUV

t(ms)

50

100

150

200

-50

0

ACC(G)

HIC=931.8

0 10 20 30 40 50

X

Y

Z

SUV

t(ms)

50

100

150

200

-50

0

ACC(G)

HIC=931.8

0 10 20 30 40 50

X

Y

Z

.ZX

Y


(Side View).

ZX

Y..

ZX

Y


(Side View)

Fig. 8 Head Acceleration diagrams for Impactor tests


the case of hood contact for the SUV, it is higher. The main factors causing the difference between

them are considered.

1. In the dummy test, because the head contact velocity is lower than vehicle speed (40km/h), the

kinetic energy is lower than for the impactor which runs 40km/h constantly. The cause of head

velocity decrease is considered as being effected by the dimension between pedestrian height and

vehicle front shape which Okamoto Y. et al. discussed [9]. The SUV hits the dummy at a higher point

because the bumper height and the hood edge height are higher than that of the passenger car. And that

hitting point comes near to the dummy center of gravity, the rotational mode is small and the head

velocity to the vehicle becomes low.

2. In the impactor test, the main acceleration is only one direction and HIC is calculated with it. But in

the dummy test, the dummy head rotates due to the contact point with the vehicle and especially the

vertical direction acceleration (Gz) occurs before the head contacts. Figure 9 shows the Gz diagram

and the dummy motions. Starting the head rotation, Gz occurs. The acceleration similar to the

impactor test is the lateral direction (Gy) in the dummy test and it occurs just after the head contact to

the vehicle like for the impactor test. So in the dummy test the HIC is calculated with three directional

accelerations which include the additional two directions not included in the impactor test and they

occur before the head contact.

-20

0

20

100

ACC (G)

0 20 40

40

60

80

60 80 100 120 140

t(ms)

Passenger Car

20 40 60 80 100 120 140

t(ms)

SUV

-20

0

20

100

ACC (G)

0

40

60

80

-20

0

20

100

ACC (G)

0 20 40

40

60

80

60 80 100 120 140

t(ms)

Passenger Car

-20

0

20

100

ACC (G)

0 20 40

40

60

80

60 80 100 120 140

t(ms)

Passenger Car

20 40 60 80 100 120 140

t(ms)

SUV

-20

0

20

100

ACC (G)

0

40

60

80

20 40 60 80 100 120 140

t(ms)

SUV

-20

0

20

100

ACC (G)

0

40

60

80

Fig. 9 Head position and Gz diagrams


To confirm their influence, the HIC with the only acceleration which occurs after the head contact is

calculated. It is used Gy for passenger car and for SUV the resultant of Gx and Gy because Gx is large

due to the forehead contact. The result is HIC=405.3 for the passenger car and HIC=356.8 for the

SUV. That shows the acceleration before the head contact is important.

3. Above HIC is calculated with the acceleration after head contact and is expected to be similar to the

impactor HIC. But for the passenger car it is higher and for the SUV it is lower than the impactor HIC.

On the SUV test, the decrease of head velocity is considered to be the reason but for passenger car

even though the head velocity decreases, it is higher. The accelerations after head contact,

(Gy :passenger car, Gx+Gy:SUV) are compared to the main acceleration of the impactor and they are

shown in Figure10. In those diagrams, impactor test 0ms timing is transferred to the head contact

timing when Gy starts to occur. These figures show that the trend of the two is similar and both first

accelerations are higher in impactor tests but the later acceleration is higher for the passenger car with

the windshield contact and lower in the SUV with the hood contact.

The difference of the first ones are considered that for the passenger car the windshield is

cracked by the dummy shoulder contact to the windshield lower part and the head contact area has

already some cracks and for the SUV the 40% decrease of head velocity is the main reason. The

difference of the later ones are considered that the head effective mass might be varied. Because the

acceleration after the head contact is caused by the force from the vehicle and the contact point is the

same rigidity as the impactor test, the mass is changed due to the external neck force. The effective

mass is estimated with the test data as follows.

The simple model which shows the situation for head contact to the vehicle is considered in Figure11.

The motion equations of the head are shown for the passenger car and the SUV respectively,

yMFFF dwydwzw&&=−+−+ )cos()sin( θθθθ

yMFFF dhydwzh&&=++++ )cos()sin( θθθθ

:Passenger Car

:SUV---(1)

yMFFF dwydwzw&&=−+−+ )cos()sin( θθθθ

yMFFF dhydwzh&&=++++ )cos()sin( θθθθ

:Passenger Car

:SUV---(1)

130 140 150 160

t(ms)

120

50

100

150

200

ACC (G)

0

Dummy Gy

Impactor Gz

Passenger Car

120 130 140 150

t(ms)

110

50

100

150

200

ACC (G)

0

Dummy Gx+Gy

Impactor Gz

SUV

130 140 150 160

t(ms)

120

50

100

150

200

ACC (G)

0

Dummy Gy

Impactor Gz

Passenger Car

130 140 150 160

t(ms)

120

50

100

150

200

ACC (G)

0

Dummy Gy

Impactor Gz

Passenger Car

120 130 140 150

t(ms)

110

50

100

150

200

ACC (G)

0

Dummy Gx+Gy

Impactor Gz

SUV

120 130 140 150

t(ms)

110

50

100

150

200

ACC (G)

0

Dummy Gx+Gy

Impactor Gz

SUV

Fig. 10 Dummy Gy or Gx+Gy and Impactor Gz diagrams


From (1), the force by the vehicle, windshield force (Fw) and hood force (Fh) is solved,

The impactor gets the only force from the vehicle, so the head effective mass which is

considered for the impactor in equ.(2) is the [ ] member. Therefore the force from the neck (Fy, Fz)

and the head contact angle is affected by the dummy motion and the windshield or hood angle are

caused by the effective mass. With equ. (2) the effective masses are estimated. Here the head angle is

analyzed by the head contact timing from the film and used constantly. There is much difference

between the vehicles. The reason is considered to the vehicle front shape and the angle of the contact

object, hood or windshield. For SUV, the dummy is hit near the pelvis so is not carried over to the

vehicle and starting to fall. Furthermore the contact object is the hood which is nearly horizontal and

consequently the contact angle is large. On the other hand, for passenger car, the dummy is carried

over and the whole body wraps around

the hood. The contact object is the

windshield which has an initial angle

so that the contact angle is small. [9]

Each constant is shown in Table4, the 4.374012SUV

4.37730Passenger Car

Actual Mass

(kg)

Dummy Head

Angle (deg)

Windshield /Hood

Angle (deg)

4.374012SUV

4.37730Passenger Car

Actual Mass

(kg)

Dummy Head

Angle (deg)

Windshield /Hood

Angle (deg)

Table 4. Value for effective mass calculation

−−

−−=

y

F

y

FMyF

dwydwzw

&&&&&&

)cos()sin( θθθθ

---(2)

+−

+−=

y

F

y

FMyF

dhydhzh

&&&&&&

)cos()sin( θθθθ

:Passenger Car

:SUV

−−

−−=

y

F

y

FMyF

dwydwzw

&&&&&&

)cos()sin( θθθθ

---(2)

+−

+−=

y

F

y

FMyF

dhydhzh

&&&&&&

)cos()sin( θθθθ

:Passenger Car

:SUV

Z

Y

X+

Fy

Fz

W/S

dθwθ

dw θθ −

Fw

Md

Z

Y

X+

Fy

Fz

dθ

hθdh θθ +

Hood Md

Fy:Upp Neck Force-y

Fz:Upp Neck Force-z

Md:Dummy Head Mass

Fw:WindShield Force

:Hood Anglehθdθ :Dummy Head Angle

wθ :WindShield Angle

Fh

Z

Y

X+Z

Y

X++

Fy

Fz

W/S

dθwθ

dw θθ −

Fw

Md

Z

Y

X+

Fy

Fz

dθ

hθdh θθ +

Hood Md

Z

Y

X+Z

Y

X++

Fy

Fz

dθ

hθdh θθ +

Hood Md

Fy:Upp Neck Force-y

Fz:Upp Neck Force-z

Md:Dummy Head Mass

Fw:WindShield Force

:Hood Anglehθ :Hood Anglehθdθ :Dummy Head Angledθ :Dummy Head Angle

wθ :WindShield Anglewθ :WindShield Angle

Fh

Fig. 11 Simple models for Effective mass


neck force diagram is shown in Figure12 and the estimated effective mass calculated with them is

shown in Figure13. For the passenger car the neck force Fz is large and plus (tension) so the effective

mass shows a tendency to decrease and for the SUV the neck force Fz is small and minus

(compression) so it shows a tendency to increase. For the passenger car, the effective mass is estimated

to be around 2 or 3kg in Figure 13 so an impactor test with the EuroNCAP Child impactor whose

weight is 2.5kg was conducted. The comparison of the acceleration – deformation diagram with the

Dummy, the Adult impactor and the Child impactor, is shown in Figure14.

In these tests, windshields with the same force deformation properties are of course used. This means

that for each test with the same deformation, the force is also the same. That is

Here suffix means d:Dummy, a:Adult Impactor and c:Child Impactor.

The masses of adult impactor and child impactor are known so the estimated effective mass of dummy

head Md is

ccaadd MMMF ααα ===

c

d

ca

d

ad MMM

α

α

α

α==

-500

1500

Force (N)

0 20 400

500

1000

60 80 100 120 160

t(ms)

Upper Neck Force Fy

(Shearing Force)

140

Passenger Car

SUV

-2000

6000

Force (N)

0 20 400

2000

4000

60 80 100 120 160

t(ms)

Upper Neck Force Fz

(Axial Force)

140

Passenger Car

SUV

Head contact timing / : Passenger Car : SUV

+: Tension

-: Compression -500

1500

Force (N)

0 20 400

500

1000

60 80 100 120 160

t(ms)

Upper Neck Force Fy

(Shearing Force)

140

Passenger Car

SUV

-500

1500

Force (N)

0 20 400

500

1000

60 80 100 120 160

t(ms)

Upper Neck Force Fy

(Shearing Force)

140

Passenger Car

SUV

-2000

6000

Force (N)

0 20 400

2000

4000

60 80 100 120 160

t(ms)

Upper Neck Force Fz

(Axial Force)

140

Passenger Car

SUV

-2000

6000

Force (N)

0 20 400

2000

4000

60 80 100 120 160

t(ms)

Upper Neck Force Fz

(Axial Force)

140

Passenger Car

SUV

Head contact timing / : Passenger Car : SUVHead contact timing / : Passenger Car: Passenger Car : SUV: SUV

+: Tension

-: Compression

Fig. 12 Neck Force diagrams

-4

8

0

2

6

-2

4

110 120 140130 150

t(ms)

Estimated Effective Mass (Kg)

Passenger Car

SUV

Dummy Head Mass

Dummy Gy Adult_Gz

(4.8kg)

Passenger Car

Child_Gz

(2.5kg)

20 40 60 120

S(mm)

0

50

100

150

200

ACC (G)

0

-50

80 100

-4

8

0

2

6

-2

4

110 120 140130 150

t(ms)

Estimated Effective Mass (Kg)

Passenger Car

SUV

Dummy Head Mass

Dummy Gy Adult_Gz

(4.8kg)

Passenger Car

Child_Gz

(2.5kg)

20 40 60 120

S(mm)

0

50

100

150

200

ACC (G)

0

-50

80 100

Dummy Gy Adult_Gz

(4.8kg)

Passenger Car

Child_Gz

(2.5kg)

20 40 60 120

S(mm)

0

50

100

150

200

ACC (G)

0

-50

80 100

Fig. 13 Estimated Effective Mass diagrams Fig. 14 Comparison of Acceleration and Deformation diagrams

between the dummy and different mass impactors


At the steady timing, with 60mm deformation data, the effective dummy head mass is estimated from

2.7kg to 3.2kg which is smaller than actual head mass, 4.37kg. For the accident of small child to a

passenger car, the head hits to the hood and the head contact angle will be similar to the result of the

adult to SUV, Okamoto. Y et al.[9] so the effective mass is considered to be similar to this SUV case.

These three issues are the main causes for the difference between dummy and impactor evaluations.

Using a physical pedestrian dummy might initially appear to be the most obvious evaluation for

assessing a car’s pedestrian protection. But there are some issues left before regulatory use which

Lawrence G.et al[7] discussed. That is the repeatability of test results because of the dummy motion,

the head contact area, the evaluation area is depending on the dummy size so there is a need for a

dummy family of different statures and the reliability to impact the target point.

1. To avoid the scatter of dummy motion especially before head contact, the dummy setting procedure

in Figure4 is adopted and

Figure15 shows the Gz diagram

for two cases. The trend is

similar before the head contact

but depending on the elbow

contact the Gz just before the

head contact is different (see

circle area). There are only a few

repeatability tests to confirm the

cause for the difference so those

tests should be conducted

parametrically.

2. From this study it is found that the evaluation for the hood with the impactor will be severer than

with the dummy. So the impactor test can evaluate the pedestrian protection level. But for a taller

pedestrian hitting and contacting the windshield or A-Pillar, the evaluation with the dummy is needed.

-20

0

20

100

ACC (G)

0 20 40

40

60

80

60 80 100 120 140

t(ms)

Passenger Car Gz

120

160

Hea

d C

onta

ct

-20

0

20

100

ACC (G)

0 20 40

40

60

80

60 80 100 120 140

t(ms)

Passenger Car Gz

120

160

Hea

d C

onta

ct

Fig. 15 Repeatability of Head Gz diagram

90-

100

101-

110

111-

120

121-

130

131-

140

141-

150

151-

160

161-

170

171-

180

181-

190

191-

200

0

10

20

30

40

Ratio (%)

Hood Edge

Hood

Cowl area

Windshield

A-Pillar

Ground

Non-Contact

Other parts

Source:PCDS

90-

100

101-

110

111-

120

121-

130

131-

140

141-

150

151-

160

161-

170

171-

180

181-

190

191-

200

0

10

20

30

40

Ratio (%)

Hood Edge

Hood

Cowl area

Windshield

A-Pillar

Ground

Non-Contact

Other parts

90-

100

101-

110

111-

120

121-

130

131-

140

141-

150

151-

160

161-

170

171-

180

181-

190

191-

200

0

10

20

30

40

Ratio (%)

Hood Edge

Hood

Cowl area

Windshield

A-Pillar

Ground

Non-Contact

Other parts

Hood Edge

Hood

Cowl area

Windshield

A-Pillar

Ground

Non-Contact

Other parts

Source:PCDS

Fig. 16 Pedestrian Height distribution for AIS 5+ Head Injury


Figure16 shows the pedestrian height distribution for AIS 5+ head injury and the height 160 – 180cm

is most prominent which is close to the AM50 size. Okamoto Y. et al [9] shows that the head contact

velocity becomes higher by an increasing pedestrian height but it is saturated around AM50 height.

And the rigidity of windshield or A-Pillar is stiffer in its lower region so the present AM50 size

dummy can cover the evaluation for the pedestrian protection level for the larger pedestrian ( AM95 )

area.

3. It is difficult to impact the dummy head to the target point. Especially to hit the A-Pillar, it is

necessary to conduct some tests to confirm the dummy motion before the final test. So it would need

much time to get the final results.

The impactor test can evaluate the protection level for the hood but to evaluate the windshield or

A-Pillar protection level, another evaluation method will be needed (reconsidering the impactor mass

or injury criteria etc.), Lawrence G. et al.[9] discussed the improvement of the current impactor.[8]

CONCLUSION

For the evaluation of head injury, the tests with the pedestrian dummy and the impactor are

conducted and the main factors causing the difference between them are considered.

1. The dummy head injury is affected by the dummy motion which is depending on the vehicle front

shape. So for the passenger car, the head contacts to windshield, the dummy HIC is higher and for the

SUV, the head contacts to hood, the dummy HIC is lower than the impactor HIC. The main causes for

those differences are the head impact velocity, three directional accelerations for HIC and head

effective mass.

2. Especialy the evaluation for windshield and A-pillar of a passenger car with the current impactor

test is considered not to be sufficient. There are some issues left for using the pedestrian dummy, so

the current test procedure with the impactor is considered to need improvement.

3. For conducting the pedestrian dummy tests to the A-Pillar, a more adaptable test procedure should

be considered in the future.

ACKNOWLEGEMENT

For pedestrian protection research it is important to understand the pedestrian accident in real

life. The accident data base Pedestrian Crash Data Study (PCDS) is very useful for the researchers.

The authors thank the National Highway Traffic Safety Administration for their efforts and for making

the data available.

REFERENCES

[1] Akiyama A., Okamoto M., Rangarajan N., "Development and application of the new pedestrian

dummy” Paper 463, 17th Conference on the Enhanced Safety of Vehicles, 2001

[2] Crandall J., Wiley K., Longhitano D., Akiyama A., "Development of performance foe a pedestrian

research dummy", Paper 05-0389, 19th Conference on the Enhanced Safety of Vehicles, 2005

[3] European Enhanced Vehicle-safety Committee, "Improved test methods to evaluate pedestrian

protection afforded by passenger cars", EEVC Working Group 17 Draft Report, 1998

[4] Isenberg R., "Final report – The Pedestrian Crash Data Study", Paper 248, 17th Conference on the

Enhanced Safety of Vehicles, 2001

[5] Ishikawa T., Kore H., Furumoto A., Kuroda S., "Evaluation of pedestrian protection structures


using impactors and full-scale dummy tests", Paper 271, 18th Conference on the Enhanced Safety

of Vehicles, 2003

[6] Kerrigan J., Kore H., Murphy D., Kam C., Bose D., Crandall J., "Kinematic corridors for PMHS

tested in full-scale pedestrian impact tests", Paper 05-0394, 19th Conference on the Enhanced

Safety of Vehicles, 2005

[7] Lawrence G.," The next steps for pedestrian protection test method ", Paper 05-0379, 19th

Conference on the Enhanced Safety of Vehicles, 2005

[8] Mizuno Y., "Summary of IHRA pedestrian safety WG activities (2005) – Proposed test method to

evaluate pedestrian protection afforded by passenger cars", Paper 05-0138, 19th Conference on the

Enhanced Safety of Vehicles, 2005

[9] Okamoto Y., Sugimoto T., Enomoto K., Kikuchi J., " Pedestrian head impact conditions

depending on the vehicle front shape and its construction – full model simulation", 00 IRCOBI

Conference, 2000


a study of pedestrian head injury evaluation method

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