PEDESTRI AN LEG I NJUR I ES , THE BUMPER AND OTHER FRONT STRUCTURES

S . J . Ash to n , J . B . Pedder and G . M . Mackay Acc i dent Research Uni t Department of Transporta tion and Envi ronmental P l anni ng ; Uni vers i ty of B i rmi ngham . Great Bri tai n

ABSTRACT

The genera l pattern of i nj ury sus tai ned by a samp l e of 2 1 1 pedestri ans struck by the fronts of cars or l i ght goods vehi c l es i s descri bed. Parti cu lar attention i s pai d to the nature, cause and severi ty of the pel v i c and l eg i njuri es susta i ned The effect of bumper hei ght a nd bumper l ead on the l ocation and i nci dence of fractures caused by the bumper i s exami ned . The potenti a l for improvement i n vehi c l e front s tructure des i gn i s exami ned by compari ng the overa l l severi ty of the i nj ur ies actua l ly susta i ned, wi th the overa l l severi ty of i nj ury that woul d have been sustai ned had there been no vehi c l e i nduced l eg i njuri es .

I NTRODUCTI ON

The Acci dent Research Uni t a t B i rmingham Uni vers i ty has made three i n-depth s tudi es i n whi ch data on pedestr ian i nj uri es have been obta i ned . I n the first two s tud i e s , carried out i n Bi rmi ngham and Worcestersh i re between 1 966 and 1 968, data on 1 04 pedestri an casua l ti es were obta i ned . The methodol ogy and resu l ts of these s tudi es have been previ ous ly descri bed ( 1 , 2 , 3 ) . * The mos t recent s tudy was carri ed out i n B i rmi ngham between 1 97 3 and 1 976 . Duri ng thi s study data on 336 pedestri ans i nvol ved i n road acci dents were col l ected . The methodol ogy of thi s s tudy a nd the genera l character i s ti cs of the samp l e have been descri bed e l sewhere ( 4 ) .

From these s tudies those cases were sel ected i n whi ch the pedestri an recei ved a di rect b l ow from the front of a car or l i ght goods veh i c l e based on a car : 2 1 1 of the 440 pedes tri ans fu l fi l l ed th is cri teria . N i nety s i x ( 9 6 ) of the pedestri ans were chi l dren, 63 were a du l ts a nd 52 were e l derly adu l ts . A chi l d has been defi ned as a person aged l es s than or equal to 1 4 years o l d , a nd an e l der ly adu lt a s a person aged greater than or equa l to 60 years o l d .

I n the resu l ts presented i n thi s paper the effects o f unknowns have been taken i nto account i n ca l cu l a ti ng percentages . Where there were unknowns the correspondi ng percentage has been wri tten i n the fonn ' a ( b-c ) ' where ' a ' i s the percentage ca l cu l a ted by el imi na ti ng the unknown va l ues and ' b ' and 1 c 1 are the percentages ca lcu l ated by a s s i gni ng ei ther a l l or none of the unknowns i nto the c l a s s under consi derati on . Thus the i nc i dence of the i tem under consi derati on wi l l l i e between ' b ' a nd ' c ' a nd wi l l probab ly be near ' a ' .

THE SAMPLE

The mai n character i st i c s of the samp l e have been prev iously descri bed ( 4 ) . Overa l l 49% of the pedestri ans were wa l ki ng i0111ed i a tely prior to impact,

*Numbers i n parentheses des i gnate references a t the end of the paper

) J

TAllLE l ACTION OF PEDESTRIAN AT IMPACT BY AGE OF PEDESTRIAN FOR PEDESTRIANS STP.UCJ: BT THE Fll.ONTS OF CARS AND LIGHT GOODS VEHICLES

AGE GROUP

MOVEMENT OF PEDESTRIAN 0-14 15-59 60+ ALL N % N % N % N %

Walking 21 21. 9 38 6 0 . 3 44 89 . 6 103 48 , 8 Runnin� 6 7 69.8 16 25.4 4 7 , 7 87 4 1 . 2 Moving speed not known 4 4 . 2 3 4 . 8 2 3 . 8 9 4 , J Stationary - standing 2 2 . 1 3 4 . 8 2 J , 8 7 3 . J Stationary - lying down - - l 1 . 6 - - l 0 , 5 Other and not known 2 2 . 1 2 3 . 2 - - 4 l . 9

96 63 52 211

41% were runni ng , 3% were stand i ng sti l l , 1 % were l yi ng i n the road and i n 6% the exact behav i our cou l d not be determi ned . Tbe behaviour of the pedestrian was found to vary wi th age . The majori ty of the chi l dren were runni ng at impact whi l st adu l ts and e l derly adu l ts were norma l l y wal k i ng : 70% of the chi l dren , 25% of the adul ts and 8% of the el der ly adul ts were descri bed a s runni ng at impact (Tab l e 1 ) .

Nearly a l l ( 911 ) the pedestrians were cross i ng the road when struck : of those cros s i ng just over ha l f ( 55%) were cro s s i ng from the Rears ide .

Approximately two thi rds (69%( 5 5%-75% ) ) of the vehi c l e s i nvo l ved were consi dered to be decel erati ng pri or to impact . A v i s i b l e s k i d mark was l eft on the road s urfqce i n 64% ( 59%-67%) of the cases where the vehi c l e was decel er­a ti ng ( Tab l e 2 ) . Deta i l s of the procedures used i n the assessment of i mpact speed have been previous ly described ( 4 ) . Overal l 1 2% of the cases occurred a an impact speed of l es s than 20km/h , 57% between 2 1 and 40km/ h , 25% between 41 and 60km/h and 4% at speeds greater than 60km/h (Tab l e 3 ) . Exami nation of the speed d i s tri butions by age showed that there were d i fferences between the d i fferent age groups : the acci dents i nvestigated i nvol v i ng chi l dren had a s l ower s peed d i s tri bution than those i nvol v i ng e l derly adul ts ; the acci dents i nvo l v i ng adul ts had a faster speed d i s tri buti on than ei ther the chi l dren or e l derly adul t s peed d i s tri buti ons . These d i fferences are probably· due to s ampl i ng d i fferences rather than real di fferences between the impact experi ence of the three age groups .

TABLE 2 ACTION OF VEHICLE AT IMPACT BY AGE OF PEDESTRIAN P'OR PEDESTRIANS STRUCK BY THE P'RONTS OF CARS AND LIGHT GOODS VEHICLES

AGE GROUP

ACTION OF VEHICLE 0-14 15-59 60+ ALL

N % N % N % N %

No braldng 3 3 . 1 9 1 4 . 3 5 9 . 6 1 7 8 . 1 Braking - before impact 18 18. 7 2 3 . 2 3 5 , 8 23 1 0 . 9

- aiter impact 10 10.4 4 6 . 3 6 1 1 . 5 20 9 . 5 - time not lmown 10 10. 4 6 9 . 5 5 9 . 6 21 10 .0

Skidding- before impact 44 4 5 . 8 29 46.0 20 38. 5 93 44 . l - after impact 5 5 . 2 2 3 . 2 6 l l . 5 1 3 6 . 2 - time not known 2 2 . 1 2 3 . 2 4 7 . 7 8 3 . 8

Otber - - l 1 . 6 l 1 . 9 2 0 . 9 Not known 4 4 . 2 8 12 . 7 2 3 . 8 1 4 6 . 6

9 6 6 3 52 211

TABLE 3 IMPACT SPEED DISTRIBUTION BY PEDESTRIAN AGE FOR PEDESTlUANS STRUCK 8Y TBE P'RONTS OP CARS AND LIGHT GOODS VEHICLES

AGE GROUP

MEAN IMPACT SPEED 0-14 15-59 60+ ALL km/h N % N % N % N %

0 - 20 19 19.8 4 6 . 3 3 5 . 8 26 12 . 3 21 - 40 59 6 1 . 5 33 5 2 . 4 39 75.0 121 5 7 . 3 4 1 - 60 16 16. 7 18 2 8 . 6 18 34 . 6 52 2 4 . 6

61+ l l . O 6 9 . 5 2 3 . 8 9 4 . 3 Not known l l . O 2 3 . 2 - 3 l . 4

96 63 52 211

Over ha l f ( 51 % ) the chi l dren , 30% of the adu l ts and 1 0% of the el derly adul ts susta i ned ei ther no i njury or mi nor i nj uri es (A IS 0-1 ) . I n four cases i t was not known whether the i nvol ved pedestri an had sustai ned a mi nor i njury or had not been i nj ured . These cases have been c l a s s i fi ed as not known . L ife threateni ng or fatal i nj uri es (A IS 4-6 ) were sustai ned by 5% of the chi l dren , 33% of the adul ts and 48% of the el derly adul ts i n the samp l e (Tabl e 4 ) .

TABLE 4 OVERALL INJURY SEVERITY (AIS) BY PEDESTRIAN AGE FOR PEDESTlUANS STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VEHICLES

AGE GROUP

INJURY SEVERITY 0-14 15-59 60+ ALL AIS N % N % N % N %

No inj ury 3 3 . 1 0 - l 1 . 9 4 l . 9 Minor 4 3 4 4 . 8 18 2 8 . 6 4 7 . 7 65 30.8 Hoderate 31 3 2 . 3 1 7 2 7 . 0 7 1 3 . 5 55 26 . l Severe 11 1 1 . S 6 9 . 5 18 3 4 . 6 35 1 6 . 6 Serious 0 o.o l 1 . 6 2 3 . 8 3 1 . 4 Critical 4 4 . 2 13 20.6 14 2 6 . 9 31 14. 7 Maximal l l . O 7 1 1 . l 6 1 1 . 5 14 6 . 6 Not ltnown 3 3 . 1 l 1 . 6 0 o . o 4 1 . 9

96 63 52 211

PATTERN OF I NJURY

I n descri b i ng the pattern of i njury the fol l owi'ng conventi ons have been adopted . For those susta i ni ng i njuries of overal l severi ty s l i ght (A IS 1 ) a l l the i nj ur ies were counted , for those susta i n i ng i nj uries of overa l l severi ty ser iou s ( non-fatal A IS 2-5 ) only the non-mi nor i nj uri es (A IS 2-5) were counted and for those susta i ni ng fatal i njuri es only the l i fe-threateni ng or fatal i nj uries (A IS 4-6 ) were counted . Thi s procedure was adopted a s i t was thought to g i ve the best overa l l pi cture o f the rel at i ve importance of the d i fferent i nj uri es susta i ned .

Leg i nj uri es were the i njuries most frequently sustai ned by those sustai n i ng s l i ght i njuri es : 74% su stai ned l eg i njuri e s , 60% head i nj uries and 32% arm i nj uri es . As the overa l l severi ty of the i njuries susta i ned i ncreased the importance of head i njuri es i ncreased : 67% of those seri ous ly i njured and 73% of those k i l l ed susta i ned a head i nj ury . Leg i nj uries were the second mos t frequent non-mi nor i nj ury sustai ned by those rece i vi ng seri ous i njuries ( Tab l e 5 ) . 35"

TABLE 5 PERCENTAGE DISTRIBUTION OF INJURIES BY SEVERITY OF INJURY FOR PEDESTRIANS STRUCK BY THE

FRONTS OF CARS AND LIGHT GOODS VEHICLES

OVERALL INJURY SEVERITY

BODY AREA SLIGHT SERIOUS FATAL

HEAD including FACE 6 0 . 0 6 7 . o 7 3 . 2

NECK t . 5 o . o 2 4 . 4

CHEST 6 . 2 2 . 1 24 . 4

ABDOMEN 7 . 7 5 . 2 1 7 . l BACK 9 . 2 5 . 2 -PELVIS 6 . 2 19 . 6 -ARMS 32 . 3 1 7 . 5 -LEGS 7 3 . 8 5 2 . 6 -

LEG I NJUR I ES

I nj uri es to . the pel v i s have been i nc l uded wi th l eg i nj uri es a s the nature of the contacts resul ti ng i n pel v i c i njury are s imi l ar to those produc i ng upper l eg i nj ur ies . I n ana lys i ng the i njuri es to the l egs a total of n i ne body reg i ons have been u sed . The regi ons correspond to the s kel etal structure and were ' pe l v i s ' , ' l eft femur ' , ' l eft knee ' , ' l eft ti b i a and fibul a ' , ' l eft ankl e and foot ' , ' ri ght femur ' , ' ri ght knee ' , ' ri ght ti bi a and f ibu l a ' and ' ri ght ank l e and foot ' . Al though the reg ions have been descri bed mai nly i n terms of skel etal structure they i nc l ude the soft t i s sue and s k i n surround i ng the boneo The most severe i njury to each region from contact wi th ei ther the veh i c l e or the ground was noted .

Pe l v i c or l eg i njuries were susta i ned by 72 chi l dren, 56 adul ts and 51 el derly adu l ts : mi nor i nj uries were sustai ned by 7 1% of the c h i l dren , 46% of the adul ts and 22% of the e l derly adul ts susta ; ni no i n i i l rv

Contact wi th the vehi c l e was respons i b l e for 7 1 % ( 63%-74%) of a l l the pe l vi c or l eg i nj uri es . The importance of the vehi c l e a s a cause of i nj ury was found to vary wi th the sever i ty of i nj ury : overal l 50% (42%-58% ) of the mi nor pel vi c or l eg i nj uri es compared to 99%(93%-99%) of the non-mi nor pel v ic or l eg i njuries were caused by veh i c l e contact . Mi nor i nj uri es to the ' pe l v i c ' , ' femur ' , or ' ti b i a/fi bu l a ' were caused ma i nly by veh i c l e contact whi l st mi nor i nj uri es to the ' knee ' or ' ank l e and foot ' resu l ted ma in ly from ground contact : 84% ( 76%-85%) of the mi nor i nj uri es to the 1 pe l vi s 1 , ' femur ' or ' ti b i a/fibu l a ' a nd 1 6% ( 1 3%-34%) of the mi nor i nj uri es to the 1 knee 1 or ' ankl e a nd foo t ' resu l ted from veh i c l e contact . ·

Vi rtua l ly a l l ( 98% ) of the pos i t ively i denti fied ground contact i nj ur ies to the pel vi s or l egs were mi nor i njuri es .

Knee i nj uri es were the mos t frequent type of mi nor pel v ic or l eg i nj ury s us ta i ned accounti ng for 42% of these i nj uri es . Femur i njuri es were the most frequent non-mi nor pel vi c or l eg i nj ury s us tai ned by chi l drec For adul ts and e l der ly adu l ts tibi a/fi b u l a i nj ur ies were the predomi nant non-mi nor pel v i c or l eg i nj ur ies . The second mos t frequent non-mi nor pel v ic or l eg i nj uri es s ustai ned by adu l ts were i nj uri es to the femur . For el derly adu l ts however pel v ic i nj uri es outranked femur i njuri es as the second mos t important non-mi nor pel v i c or l eg i njury ( Tab l e 6 ) .

Fractures were the predomi nant non-minor pel v ic or l eg i njur i es accounti ng for 88% of these i nj uri es : a l l the non-mi nor pel v ic or l eg i nj ur ies s us tai ned by chi l dren , 78% of those s us ta i ned by adul ts and 89% of those s us ta i ned b�

TABLE 6 LOCATION, GENERAL CAUSE AND SEVERITY OF PELVIC AND LEG INJURIES SUSTAINED BY PEDESTRIANS STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VEHICLES

a) children

MINOR INJURIE$ NON-MINOR INJURIES

N % VEHICLE N % VEHICLE

PELVIS 4 100 6 100

FEMUR 20 84(80-85) 11 100

KNEE 5 1 9 ( 8-14) 1 100

T!BIA AND FIBULA 19 56 (53-58) 9 100

ANKLE AND FOOT 9 0 ( 0-22) 0 -

OVERALL 103 3 7 ( 33-44) 2 7 100

b) adults

MINOR INJURIES NON-MINOR INJURIES

N % VERICLE N % VEHICLE

PELVIS 5 7 5 ( 60-80) 9 100

FEMUR 1 7 82 17 9 3 ( 82-94)

KNEE 27 37(26-56) 5 100(80-100)

TIBIA AND FIBULA 1 7 94 20 100

ANKLE AND FOOT 10 40(20-70) 0 -

OVERALL 76 6 8 ( 55-74) 51 98( 92-98)

c) elderly ad�lts MINOR INJURIES NON-MINOR INJURIES

N � VEHICLE N % VEHICLE

PELVIS - 2 3 100(96-100)

FEMUR 9 100(89-100) 19 100(84-100)

KNEE 1 9 6 ( 5 - 1 6 ) 2 100(50-100)

TIBlA AND FIBULA 1 7 100(65-100) 3 5 9 7

ANKLE AND FOOT 9 29(22- 44) 5 100(80-100)

OVERALL 54 5 1 (41- 6 1 ) 84 9 9 (92- 99)

'I'.ABLE 7 SPECIFIC CAUSE OF NON-MINOR PELVIC AND LEG INJURIES BY PEDESTRIAN AGE FOR PEDESTRIANS STRUCK BY TRE FRONTS OF CARS AND LIGHT GOODS VEHICLES

AGE GROUP

CAUSE OF INJURY 0-14 15-59 60+ ALL

N % N % N % N %

Bumper 18 66 . 7 2 5 5 3 . 2 40 5 1 . 9 83 5 5 . 0

Headlight surround/radiator grill 4 1 4 . 8 2 4 . 3 3 3 . 9 9 6 . 0

Leading adge of wing/bonnet 5 1 8 . 5 18 38 . 3 32 4 1 . 6 5 5 36 . 4

Other 0 - 2 4 . 3 2 2 . 6 4 2 . 6

VEHICLE CONTACT 2 7 100 . 0 47 1 00 . 0 7 7 100.0 151 100 . 0

GRQUND CONTACT 0 l l 2 NOt' KNOWN 0 3 6 9

2 7 5 1 84 1 6 2

el derly adul ts were fractures . Surface i nj uri es accounted for a further 9% and joi nt i njuri es for 3% of the non-mi nor pel v ic or l eg i njuri es .

Contact wi th the bumper was the mai n cause of veh i c l e contact non-mi nor pel vi c or l eg i njuri es bei ng respons i b l e for 55% of a l l s uch i njuri e s . Contact wi th the front s tructure above the bumper, parti cul arly the l eadi ng edge of the bonnet or wi ngs was the next most frequent cause bei ng respons i b l e for a further 36% of the veh i c l e contact non-mi nor pel v ic or l eg i nj uries ( Ta b l e 7 ) .

The i nc i dence and sever i ty of the i nj uri es sustai ned was re l a ted to i mpact s·peed : overa l l 54% of the pedes tri ans i n the speed range 0-20km/ h , 85% i n the range 2 1 - 40km/h and a l l those s truck at speeds above 60km/h s ustai ned a pel v ic or l eg i nj ury . For non-mi nor i njuri es the comparab le fi gures were 4%, 42%, 63% and 89% ( Tab le 8 ) . Th i s i ncrease i n i nj ury sever i ty wi th i mpact speed was so lely due to an i ncrease i n the severi ty of vehi c l e contact i njuri es wi th impact speed: vi rtua l ly a l l the ground contact i nj uri es bei ng mi nor i nj uri es .

Age had an important effect on the sever i ty of the pel v ic and l eg i njuri es sustai ned , the o l der the pedes tri an then the more l i kely were the i nj uri es to be seri ous . In the 2 1 -40km/h speed range non-mi nor pel vi c or l eg i njuri es were susta i ned by 1 9% of the chi l dren , 39% of the adul ts and 88% of the el derly adu l ts : the di fferences between chi l dren and adul ts were just not s i gni fi cant at

TABLE 8 OVERALL SEVERITY OF PELVIC AND LEG INJURIES

a) Children

IMPACT SPEED km/h 0

0 - 20 8 21 - 40 15 41 - 60 l

6 1 +

2 4

b ) Adults

L"IPACT SPEED km/h 0 0 - 20 3

21 - 40 3 41 - 60 l

6 1 +

7

c) Elderly adults

IMPACT SPEED km/h 0

0 - 20 l 21 - 40 41 - 60

61+

l

1 1

INJURY SEVERITY AIS

l 2 3 ALL

l l 19 33 10 l 59

6 4 5 16 l 1

50 14 7 95

INJURY SEVERITY AIS

l 2 J All

1 4 1 7 7 6 33

7 4 6 18 1 5 6

26 1 1 1 7 6 1

INJURY SEVERITY AIS

1 2 J ALL

l l J 6 s 18 29 4 2 12 18

2 2

1 1 8 32 52 s 2 .,.

the 5% l evel ( X2,jt-1 = 3 . 71 ) whi l s t there were h i gh ly s i gni fi cant di fferences between the adul ts and e l derly adul ts ( X2 d\• ' = 8 . 53 ) . I n the 4 1 -60km/h speed range 78% of the el derly adu l ts sustai ned non-mi nor pel v ic or l eg i nj uri es compared to 56% of both the ch i l dren and adu l ts : these di fferences were not s i g n i fi cant for adu l ts a nd e l der ly adu l ts x2 J� 1 = 1 . 1 3 . Simi l ar trends were observed wi th the severe (A IS 3 ) i nj uri es ; i n the 2 1 -40km/h range 2% of the chi l dren , 1 8% of the adul ts and 62% of the e l derly adu l ts recei ved a severe pe l vic or l eg i nj ury .

FACTORS I NFLUENC ING LEG I NJURIES

The i nf l uence that the des i gn of the veh i c l e structure , and i n part icu lar the l ocation of the bumper can have on the nature and l ocation of the l eg i nj uri es was exami ned by con s i deri ng the variations i n l eg i njuries sustai ned by pedestrians i n th i s samp l e struck by vehi c l e s hav i ng di fferi ng bumper hei ghts a nd bumper l eads .

I n exami n i ng the effect of bumper l ocation the pos i t i on of the bumper has been defi ned wi th respect to the height of the struck pedestri an to enab l e compari sons to be made on a standardi zed bas i s . The rel at ive bumper height has been defi ned a s :

RELATIVE BUMPER HE I GHT = ABSOLUTE BUMPER HE I GHT PEDESTRIAN AEIGAT

I n a s imi l ar way the hei ght of the l eadi ng edge of the veh i cl e ' s bonnet or wi ngs has been defi ned a s :

RELAT IVE LEADING EDGE HE I GHT = ABSOLUTE LEADING EDGE HE IGHT PEDESTRIAN AEIGAT

As the contact between the bumper and the struck pedestri an can be i nfl uenced by the l ocation of the l eadi ng edge of the bonnet or wi ngs , the l ocation of the l ead i ng edge has been rel a ted to the l ocation of the bumper i n terms of f i rst the d i fference i n height of the l eadi ng edge and the bumper and second the bumper l ead . Thi s has been defi ned as :

BUMPER LEAD ANGLE • Tan-1 ( LEADING EDGEB�A���TLEA�UMPER H E I GHT ) Fi gure 1 i l l ustrates tbe defi ni tions used by r.eference to a s ty l i zed vehi c l e .

I NFLUENCE O F BUMPER LOCAT ION ON LOCAT ION OF FRACTURES

A tota l of 75 l eg fractures were a ttri buted to bumper contact : femora l s ha ft fractures accounted for 9 ( 1 2% ) , fractures to the knee , defi ned as i nc l udi ng the femoral condy l es and ti b i a l head , a ccounted for 1 1 ( 1 5% ) and fractures to the t ib ia and/or fi b u l a accounted for 5 1 (68% ) . There was one case of mu l ti p l e fractures to the fi b u l a resu l ti ng from the pedestr ian bei ng �rapee� between the �a� front and a wa l l , and three cases ( 4%) of fractures i nvol v1 ng the ankl e J oi nt . The exact l ocati on of the fracture was known i n 58 cases .

FIGURE l

SH

La BL

DEFINATION OF VEHICLE FRONT END SHAPE PARAMETERS

• Static height of bumper

• Static height of leading ed�e of bannet • Bumper lead

&ELATIVE BIJMPER HEIGHT

RELATIVE LEAD ING EDGE HEIGHT

BUMPER LEAD ANGLE e8L

9BL • Bumper lead angle

PEDH • Pedestrian height

Static height of bumper BH

:edestrian height PED8

Static height of leading edge � Pedestrian height PED8

TABLE 9 LOCATION OF FRACTURES RESULTING FROM BUMPER CONTACT HEIGHT FOR PEDESTRL\.NS STRUCK BY THE FRONTS OF CA.RS AND LIGHT GOODS VEHICLES

RELATIVE RELATIVE BUMPER HEIGHT

LOCATION OF FRACTURE FRACTURE . 16- . .W . 21- . 25 . 2 6- . 30 . 3 1- . 35 . 36-.40 . 4 1 - . 4 5 N . K. ALL HEIGHT

FEMUR - UPPER THIRD . 41-.. 45 l l

- MID SHAIT . 36- . 40 l l 3 1 5 - LOWER THIRD . 3 1 - . 35 2 2

NOT KNOWN l l CONDYLES . 26- . 30 3 l 4

KNEE . 26- . JO 2 1 2

rIBIAL HEAD . 26-.30 2 2 l 5 !IBIA - UPPER THIRD . 21 - . 25 l 9 l l 12

AND/OR - MID SHAFT . 16- . 20 3 1 1 3 l 18

FIBULA - LOWER THIRD . 1 1- . 1 5 5 5 NOT KNOWN l 8 7 16

MULTIPLE l l

ANKLE . 06- . 10 3 3

7 2 5 2 5 9 3 4 2 75

The l ocation of the fracture was i nf l uenced by the pos i ti on of the bumper (Tab l e 9 ) : the fractures most frequently occurri ng j us t bel ow the s tatic he ight of the bumper . Compari son of the rel ati ve fracture hei gh t , defi ned i n a s imi l a r way to rel ati ve bumper height, wi th re l a ti ve bumper height showed that the fracture l ocati on a ppeared to be norma l ly di s tr i buted about a mean height one c l a s s bel ow the s ta ti c height of the bumper ( Ta b l e 1 0 ) . Thi s corresponds to an a verage d i s ta nce of about 8cms between the s ta ti c height of the bumper and the l ocation of the fracture . Th i s di fference s tems from the l ower i ng of the veh i cl e front during braki ng and a l s o from the use of unshod pedestri an height data . A l l owance of say 3cms for s hoe hei ght means that the average d i p of the veh i c l e front at impact was 5cms The vari ations i n fracture l ocation can be partly attri buted to the use of average pede str ian height i n ca l cu l a ti ng the rel a ti ve bumper hei ght and partly to the varyi ng amount of d i p of the veh i c l e front a t i mpact .

!ABLE 10 DIFFERENCE BETWEEN RELATIVE FRACTURE HEIGHT AND RELAl'IVE BUMPER llEIGHT P'Ol PEDESTRIANS STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VEHICLES

DIFFERENCE - NUMBER OF CLASSES

-2 1 - l 1 0 1 +l

12 1 28 1 l3 1 l

ANKLE AND KNEE I NJURIES

I nj uries i nvol v i ng the joi nts warrent spec i a l a ttention a s impai rment of joi nt functi on wi1 1 restri ct the mobi l i ty of a person whereas an i nj ury whi ch does not i nvo l ve a joi nt i s l e s s l i kely to cause i mpa i rment to future mobi l i ty .

Three pedestri ans susta i ned serious ankl e i njuri e s , the simi l ari ti es between the three acci dents were surpri s i ng . Al l i nvo l ved el derly adul ts struck by the same make and model of vehi c l e at impact speeds i n the regi on of 50km/h . Thi s parti cul a r veh i c l e has i ts bumper l ocated 28cms above the ground ; the rel at ive bumper heights were ei ther 0 . 1 7 or 0 . 1 8 . Al l three pedestri ans d ied . Append i x l gi ves deta i l s of the cases . The mechani sm of i nj ury i n a l l three cases appeared to be angu l at ion of the ankl e beneath the bumper .

Leg fractures were susta i ned by 6 of the 28 pedestri ans struck by veh ic l es where the rel at ive bumper hei ght was 0 . 1 6-0 . 20 : ha l f of those wi th l eg fractures susta i ned an ank l e fractu re .

E l even pedestri ans susta i ned fractures to the knee . Fractures i nvol v i ng the femoral condy les or t i b i a l head were counted as knee 1 nJur1 es . I n addi tion to these cases there was one case ( case 1 00 ) of patel l a fracture wh i ch cou l d not be defi nately attri buted to the bumper , and two cases ( cases 1 09 and 1 6 7 ) i nvol v ing rupture o f the knee joi nt l i gaments resu l ti ng from bumper contact . Al l the k nee i njuries defi nately attri buted to bumper contact occurred at mean i mpact speeds greater than 2 l km/h . I n 5 of the cases the pedestrian d i ed and i n one case the pedestr ian susta i ned serious brai n i nj uries but surv ived : these cases compri sed a l l the cases occurri ng at i mpact speeds greater than 4 l km/ h . Deta i l s o f the cases are g i ven i n Appendi x 2 .

The e l even cases of knee fracture occurred at rel ati ve bumper hei ghts of between 0 . 26 and 0 . 37 . The two cases of l i gament damage both occurred wi th veh i cl es of rel ati ve bumper hei ghts of 0 . 26 . I n s i x cases the vehi c l e was

o/1

not braki ng a t impact , i n fi ve cases the veh i c l e was braki ng and i n two cases i t cou l d not be establ i s hed whether braki ng occurred before or after i mpact (Tabl e 1 1 ) . The average rel ative bumper height for veh i c l es not braki ng was 0 . 28 and for veh i c l es bra k i ng 0 . 32 . These rel ati ve bumper hei ghts correspond to actual hei ghts of 45cm and 5 l cm for the average non-�i nor i njured pedestri an ( Average pedestri an hei ght for pedestri ans susta i ni ng non-mi nor i nj ur ies i n Great Bri ta i n = l . 6m ( 4 ) ) .

TABLE 1 1 INCIDENCE OF mEE INJURIES BY RELATIVE BUMPER HEIGBT AND VEHICLE BRAKING FOR PEDESTRIANS STRUCK BY THE

FRONTS OF CARS AND LIGHT GOODS VEHICLES

RELATIVE VEHICLE BRAKING

BUMPER NONE BRAKING NK ALL

HEIGHT

. 26-.30 5 l l 7

. 3 1 - . 35 l 3 l 5

. 36-.40 l l

6 5 2 l 3

The i nci dence of a knee i nj ury was i nfl uenced by i mpact speed . Of the 1 2 cases of knee i nj ury occurri ng from contact w i th a bumper l oca ted a t a re l a ti ve height of 0 . 26 -0 . 35 s i x occurred at i mpact speeds i n the range 2 1 -40km/h , fi ve occurred i n the range 4 1 -60km/h and one at a n i mpac t speed greater than 60km/h . These cases of knee i njury accounted for 1 1 % , 22% and 25% of the cases i n 2 1 - 40km/h , 4 1 -60km/h and 6 1 +km/h speed ranges respective ly .

To exami ne the i nfl uence of absol ute bumper hei ght on knee i nj ur ies the i nci dence of knee i njuries by absol ute bumper hei ght was considered ( Tab l e 1 2 ) . Of the 1 3 cases of k nee i njury attri buted to bumper contact 6 ( 46%) were caused by bumpers l ocated a t between 50 and 54cms from the ground, 3 ( 23% ) each by bumper l ocated at 40-44cms and 45-49cms and only 1 ( 8%) by a bumper l ocated i n the 35-39cms range . Bumpers l ocated at 50-54cms appear to be parti cu l arly prone to causi ng k nee i nj ury : 25% of a l l veh i c l e s in the sampl e wi th bumpers l ocated a t thi s hei ght caused a non-mi nor knee i njury .

The i ncreased l i kel i hood of knee i nj ury when the bumper i s l ocated at approximately 50cms above the ground has been s hown ·previous ly from a consi der­ati on of the percentage of the popul ation sustai ni ng a di rect knee contact from bumpers of gi ven wi dth and hei ght above the ground ( 4 , 5 ) .

TABLE 1 2 INCIDENCE O F mEE lNJURIES RESULTING FROM BUMPER CONTAC! BY ABSOLUTE HEIGHT O F BUMPER FOR PEDESTRIANS

STRUCK BY TBE FRONTS OF CARS AND LIGHT GOODS VEHICLES

ABSOLUTE HEIGBT OF BUMPER CMS

25-29 30-34 35-39 40-44 45-49 50-54 NK i ALL ALL CASES 31 6 4 7 5 4 4 8 24 l ! 2 1 1

KNEE INJURY 1 3 3 6 1 1 3

% KNEE INJURY 0 . 0% 0.0% 2 . 1% 5 . 6% 6 . 3% 25.0% 1 6 . 2%

I NFLUENCE OF BUMPER LOCAT ION I N I NC IDENCE OF FRACTURES

The l ocation of the bumper was found to i nfl uence the i nci dence wi th which fractures occur as wel l as the i r l ocati on . Exami nation of the i nci dence of bumper i nduced fractu res by re l at i ve bumper hei ght a nd i mpact speed s hows that there was an i ncrease i n the i nci dence of bumper i nduced fractures wi th i ncreas i ng speed : bel ow 20km/h there were no fractures from bumper contact , above 60km/h vi rtual l y a l l ( 89%) sustai ned a fracture (Tab l e 1 3 ) . There was a l so a hi gher i·nci dence of fractures for those cases where the rel at ive bumper hei ght was 0 . 2 1 - 0 . 30 than for any other rel ati ve hei ghts . The decrease i n fracture i nc i dence wi th i ncrea s i ng rel ati ve bumper height from 0 . 2 1 -0 . 30 may be exp l a i ned by the i ncreas i ng number of chi l dren i n the hi gher re l a ti ve bumper hei ght c l asses ; ch i l dren poss i b ly bei ng l es s l i ke ly to susta i n a fracture than an adu l t at a g i ven speed due to thei r l i ghter mas s . Thi s does not however exp l a i n the decrease i n fracture i nc i dence as the rel ati ve bumper height i s reduced from 0 . 21 -0 . 30 to 0 . 20 . Thi s decrease appears to be due to a decreased l i ke l i hood of l eg fracture wi th decreased rel ati ve bumper hei gh t . To exami ne thi s i n more deta i l the i nc i dence of fractures i n the 21 -40km/h speed range has been consi dered by sma l l er rel at i ve bumper height groupi ngs (Ta b l e 1 4 ) . Exami nation of thi s tab l e s hows that for chi l dren there was an i ncrease i n the i nci dence of fractures up to a rel a ti ve bumper height of 0-36-0 . 40 and then the i nci dence of fractures decreased . l t was noted earl ier that the decrease i n fracture i nci dence wi th i ncreas i ng ly rel at i ve bumper hei ght may be due to the chi l dren i n the h i gher rel ati ve bumper hei ght c l a ss es be i ng l i ghter . Cons i derati on of the age di s tri bution of the chi l dren tends to support thi s : ch i l dren under 5 years compri sed 2 1 % of the 0 . 36-0 . 40 re l a ti ve bumper he i ght group, 33% of the 0 . 41 -0 . 45 group, 60% of the 0 . 46-0 . 50 group and a l l the 0 . 51 -0 . 55 group . For adul ts there was an i ncrease i n the i nc i dence of fractures w i th i ncrea s i ng rel a ti ve bumper hei ght . For e l derly adul ts however , a l though there was an i ncrease i n fracture i nci dence from rel ati ve bumper hei ghts of 0 . 1 6-0 . 20 to 0 . 2 1 -0 . 25 there was a decrease i n fracture i nci dence at hei ghts above thi s . l t cou l d be tha t i nj ury tol erance has a confoundi ng effect i n thi s group ; there bei ng wi de variati ons i n i nj ury tol erance w i thi n the group . The fi gures i n general suggest that bumper l ocati on i nfl uences the i nci dence of fractures .

TABLE 13 INCIDENCE OF FRACTURES RESULTillG FROM BUMPER CONTACT BUMPER HEIGHT AND IMPACT SPEED FOR PEDESTRIANS

STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VERICLES

RELATIVE L'!PACT SPEED km/h BUMPER

llEIGHT 0-20 21-40 41-60 61+

< . 20 0% n•3 14% n•l4 27% n•ll 100% n•l . 2 1- . 30 0% n•l2 36% n•S6 68% n•31 100% n•4 . 3 1 - . 40 0% n•S 22% n•37 14% n•7 17% n•3 „ . 4 1 0% n•6 8% n•13 50% n•2 100% n•l

TABLE 14 INClDENCE OF FRACTURES RESULTING FROM BUMPER CONTACT BY AGE OF PEDESTRIAN AND RELATIVE BUMPER HEIGHT FOR PEDESTRIANS STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VEBICLES TRAVEU.ING AT 20-41 km/h.

AGE GROUP

RELATIVE 0-14 15-59 60+

BUMPER NO OF % WITB NO OF % WITB NO OF % WITH HEIGHT CASES FRACTURE CASES FRACTURE CASES FRACTURE

0. 1 6 - 0 . 20 2 o . o 6 0 . 0 6 3 3 . 3 0 . 21 - 0 . 25 3 o . o 1 1 2 7 . 3 7 85 . 7 0.26 - 0 . 30 12 8 . 3 1 1 2 7 . 3 12 5 8 . 3 o.:n - o . 35 14 14. 3 5 40.0 3 3 3 . 3 0.36 - 0.40 14 2 1 . 4 1 o . o 0 . 4 1 - 0 . 45 6 1 6 . 7 0.46 - 0.50 5 o.o 0 . 5 1 - 0.55 2 o . o

58 33 29

I NFLUENCE OF BUMPER LEAD ON BUMPER I NDUCED FRACTURES

The bumper l ead , or more preci sely the bumper l ead ang l e was found to i nfl uence the rel ati ve importance of the bumper and the rest of the front structure above the bumper as a cause of fractures ( Tabl e 1 5 ) . I ncreas i ng the bumper l ead for a g i ven l eadi ng edge of bonnet/wi ng hei ght , i e . decreas i ng the bumper l ead ang l e , was found to i ncrease the proportion of fractures from bumper contact : for bumper l ead ang les of 90-81 ° only 40% of those susta i n i ng fractures from contact wi th the front of a veh i c l e sustai ned only bumBer i nduced fractures whereas the comparab l e fi gure for bumper l ead angl es o fc 70 was 73% . The i nc i dence of fractures from the l eadi ng edge , e i ther a l one or i n conjuncti on wi th a bumper contact fracture , decreased wi th decrea s i ng bumper l ead ang l e frim 60% for bumper J ead angles of 90-81 0 to 27% for bumper l ead . a ng l es of

0�70 . Compar i son of the i nci dence of bumper contact fractures only i n

the 90-81 and � 700 bumper l ead ang l e groups s howed that the di fferences were just not s i gni fi cant at the 5% l evel ( p = . 0529 ) .

Bumper l ead appeared to have an effect on the i nci dence of fractures , there bei ng a h i gher i nci dence of fractures wi th decreas i ng bumper l ead angl e . I n the 2 1 - 40km/h s peed rang0 only 28% of the adul ts s truck by vehi c l e where the bumper l ead angl e was 90-81 sustai ned a fra0ture to the pel vi s or l egs compared to 5000% for bumper l ead angl es of 80-7 1 and 57% for bumper l ead angl es l es s than 70 ( Tab 1 e 1 6 ) . These di ff erences however were not .s ta ti s ti ca l ly s i gn i fi cant .

TABLE 15 INCIDENCE OF FRACTURES RESULTING FROM BUMPER CONTACT AND LEADING EDGE CONTACT BY BUMPER LEAD ANGLE FOR PEDESTRIANS STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VEHICLES

BUMPER LEAD ANGLE

9o - 81° 80 - 7 1° ' 10·

N % N % N %

FRACTURES FROM LEADING EDGE ONLY 12 26 . 7 3 1 1 . 5 2 1 8 . 2 FRACTURES FROH LEADING EOGE AND BUMPER 15 33 . 3 1 1 42 . 3 l 9 . 1 FRACTURE FROM BUMPER ONLY 18 40.0 12 46 . 2 8 7 2 . 7

" 45 26 1 1

TABLE 16 INCIDENT OF FRACTURES BY AGE OF PEDESTRIAN AND BUMPER LEAD ANGLE POR P!DKSTRIANS STRUCK BY THE FRONTS

OF CARS AND LIGHT GOOD VEHICLES TRAVELLING AT 21-40 k.m/b

ACE GROUP BUMPER

0-14 15-59 60+ LEAD

ANGLE NO OP % WITH NO OF % WITH NO OF % WITH

CA:SES FRACTURE CASES FRACTURE CASES FRACTURE

90-81.

30 19 . 4 1 8 2 7 . 8 l3 46 . 2

80-71°

1 7 1 7 . 6 8 50.0 1 2 9 1 . 7

6 70°

5 20.0 7 5 7 . l 4 7 5 . 0

58 33 29

I NFLUENCE OF LEADI NG EDGE LOCATION ON LOCATI ON OF FRACTURES

Fractures res ul ti ng from contact wi th the l eadi ng edge of the vehi c l e d i d not appear to b e a s c l osely rel ated to the rel at i ve hei ght o f the l ead i ng edge as bumper contact fractures a re to rea l ti ve bumper height ( Table 1 7 ) . The spread i n re l at i ve l eadi ng edge hei ghts for pel v i c i njuri es was greater than that for femur i njuri es .

Pos s i b l e reasons for the greater variati on i n the rel at ive contact hei ghts for femur i nj ur ies are that fi rstly the l ocation of the maximum bend i ng of the femur may not be at the l ead i ng edge height due to forces on the l eg from the i ni ti a l bumper contact . Secondly the l eadi ng edge may suffer extensi ve defonnation thus affect i ng the effective l eadi ng edge height and thi rdl y there may have been rel ati ve motion between the pedestri an and the l eadi ng edge before the l oads have bui l t up .

Simi l arly th� vari a ti on i n the rel at ive l eadi ng edge hei ghts for pel v ic i nj u ry may be i nfl uenced by the above though in the case of the pe l v i s a b low to the femur anywhere a l ong i ts l ength i s l i ke ly to resu l t i n forces bei ng transmi tted to the pel v i c ri ng through the h i p joi nt , the fracture occurri ng a t the weakest pöi nts of the system .

Fractures to the femur were seen wi th re l ati ve l eadi ng edge heights of 4 0 . 35 to 0 . 56-0 . 60 a l though the majori ty ( 86%) occurred i n the range 0 . 36-0 . 5 5 . I njur ies to the h i p , i e . trochanteri c fractures or acetabu l um fractures occurred wi th rel at i ve l eadi ng edge hei ghts of between 0 . 4 1 and 0 . 5 5 : two thi rds occurred when the rel ati ve l eadi ng edge height was i n the range 0 . 46-0 . 50 . Pel v i c fractures occurred at rel ati ve l eadi ng edge hei ghts as l ow a s � 0 . 35 or as h i gh as 0-6p-0 . 70 a l though over hal f ( 60%) o:curred i n the range 0 . 4 1 -0 . 50 .

TABLE 1 7 LOCAl'ION OF FRACTURES RESULTING FROH LE.ADING EDGE CONTACT BY RELATIVE LEADING !DGE II!IGHT FOR

PEDESTRIANS STRUCK BY THE FRONTS OF CARS AND LIGHT GOODS VEHICLES

LOCATION RELATIVE RELATIVE LE.ADING EDGE !IEIGHT

OF FRACTURE � . 35 . 36- . 40 . 4 1 - . 45 . 46-.50 . 51 - . 5 5 . 56-.60 . 6 1 - . 6 5 . 6 6 - . 70 FRACTURE HEIGHT

PELVIS .46-.60 3 3 5 13 l 4 l

ACETABULUM . 46-. so l 4 l

FEMUR - TROCHANTER . 46 - . 5 0 l 2

IJPPER THIRD . 4 1- . 45

MII>-SRAFT . 36-. 40 2 6 2 2 l

LOWER THIRD . 31 - . 35 l

NOT KNOWN l 3

4 6 1 3 24 4 5 l

ALL

30

6

3

lJ

l

4

57

Al l the cases i n wh i ch there were acetabu l um fractures i nvol ved el derly adu l ts i n wh ich the rel ati ve l eadi ng edge hei ght was between 0 . 45 and 0 . 5 1 and the bumper l ead ang l es were greater than or equal to 770 , Al l the cases occurred at impact speeds above 3 l km/h except one where there was a concentrated l oadi ng on the h i p from a headl i ght cowl . Appendi x 3 g i ves detai l s of the cases .

POTENT IAL REDUCTION I N I NJURY SEVERITY

The potenti a l benefi ts obta i nabl e by i mproved veh i c l e front end des i gn were exami ned by cons i deri ng how the overa l l severity of i nj ury wou l d have been changed had the only pel v i c or l eg i nj ury su stai ned as a resu l t of veh i c l e contact been mi nor i njuri es .

As pel vi c and l eg i njuries are rarely a cause of death i n pedestr i a n s , improvements i n front structure des i g n , i n s o far a s they i nfl uence the i n i ta l veh i cl e-pedestri an contact , wi l l not markedly affect the numbers k i l l ed .

The effect on serious i njuri es , defi ned a s non-mi nor non-fatal i nj uri es , i s s i gn ifi cant . Serious i njuri es were sustai ned by 44 chi l dren , 25 adu l ts and 28 e l derly adul ts i n thi s samp l e . E l imi nati on of the veh i c l e contact non-mi nor pel v i c and l eg i nj uries reduced the number seri ous l y i njured to 33 c h i l dren , 20 adul ts and 23 e l derly adul ts ; i e . an overa l l reduction of 22% i n the number seri ous ly i njured .

A proporti on of those serious l y i njured , however , sustai n i njuries no more serious than a bri ef period of unconsci ousness , a l l the other i njuries be i ng mi nor i nj uri es , I n exami n i ng the potenti a l benefi ts of i mproved front structure des i g n i t i s perhaps a l so worth cons i deri ng those who susta i n a non-mi nor i nj ury other than a brief peri od of unconsci ousness ; 3 1 chi l dren , 2 1 adul ts and 27 el der ly adu l ts ful fi l l ed th i s cri teri a . E l i m i nat ion of the non-mi nor veh i c l e contact pe l v i c and l eg i njur ies for these cases and a l so the e l imi nati on of those cases where the only rema i ni ng non-mi nor i nj ury was a brief peri od of unconscious­nes s , reduced the number seri ously i njured to 18 chi l dren , 1 5 adu l ts and 1 8 e l derly adu l ts . i e . an overa l l reducti on of 35% .

D ISCUSS ION

The des i gn of the front s tructure can have a s i gn ifi cant effect on the pel v i c and l ower l imb i nj uries of pedestri ans struck. by the fronts of cars . The l ocation of the bumper i nf l uences not only the l ocation but a l so the l i kel i hood of a fracture occurri ng as a resu l t of contact wi th the bumper . The optimal design i s a compromise between d i fferent facto.rs .

Knee i nj ur i es a re l i ke ly to resul t when the bumper i s l ocated at a rel ati ve height of 0 . 26-0 .35 . Reduction i n the rel at ive height of the bumper l es sens the chance of a knee i nvol vement and a l so appears to reduce the l i ke l i hood of fracture for a gi ven impact speed . However th i s has to be countered agai nst the i ncreased ri s k of ank l e i nj uries wi th l ow bumpers . Three cases of ank l e i nj ury were seen wi th bumpers l ocated at a rel at ive height of 0 - 1 6 -0 . 1 7 . l t must be s tressed that these three cases of ank l e i nj u ry a l l occurred i n h i gh s peed acc i dents , the pedestri ans sustai ni ng fata l i nj uries whereas the majori ty of the knee i njuri es occurred to non-fatal ly i nj ured pedestri ans .

The reduction i n fracture i nc idence wi th decrea s i ng rel ati ve bumper height tends to s upport the experimenta l fi ndi ngs of Bacon and Wi l son ( 6 ) who found that bumper force i ncreased w i th i ncreas i ng rel a ti ve bumper hei ght . They attrib uted

46

the i ncrease i n bumper force w i th re l a ti ve bumper hei gh t to the effecti ve mass of the l eg varyi ng wi th the l ocation of the contact. However i t must be remembered that the vari ati ons i n fracture i nci dence wi th rel a ti ve bumper l ocati on i n rea l acci dents may not be so le ly due to thi s reason : vari a ti ons i n the tol erance of the l eg a l ong i ts hei ght be ing l i kely .

The decreased i nci dence of fractures from l ead i ng edge contact wi th i ncreased bumper l ead i s a l so i n agreement wi th the experimenta l resul ts of Bacon and Wi l son . They suggest further that the des i gn of the bumper and l eadi ng edge must be consi dered together a s , a l though a reduct i on i n bumper l ead decrea ses the bumper contact forces i t has the effect of i ncrea s i ng the l eadi ng edge contact forces . Th i s phi l osophy was not fol l owed however i n the devel opment of a pro-pedestr ian front structure ; cons i derati on only bei ng g i ven to the i nvesti gati on of i mproved bumper characteri sti c s for pedestr ian protect1on . Jehu and Pearson ( 7 ) concl uded from a series of experimental tests that the l ead i ng edge s hou l d be made to be energy absorbi ng . However they sti l l conti nue to see the front structure as con s i s t i ng of a separate bumper and l ead i ng edge . Thi s may be the wrong concept for improved pedestrian protecti on . The whol e o f the vehi c l e front s tructure cou l d be desi gned to be compl i ant , the l oads be i ng d i s tributed over the l ower part of the pedes tri ans body rather than bei ng appl i ed at two poi nts by the bumper and l eadi ng edge . The Chrys l er-Ca l span RSV ( 8 ) has such a front structure and experimenta l tests compar i ng the RSV wi th conventi onal vehi c l e s ( 9 ) suggest that the fracture thresho l d may be i ncreased by as much a s 8-1 6km/ h .

Appl i cat i on of the f i gures for the reducti on i n seri ous i njur ies deri ved from thi s samp l e of acc i dents to the total popu l at ion i n Great Br it i an shows that a reduct i on of some 2000 serious i nj ury casua l ti es cou l d be expected i f vehi c l e front structures were made pro-pedestri an . Thi s assumes that the i mprovements to the front structure do not adversely affect the subsequent moti on of the pedestri a n . Pri tz ( 1 0 ) found that there was l es s spread i n the l ocation of the head i mpact wi th compl i ant front structures and thi s s hou l d be of advantage i n des i gni ng the vehi cl e exteri or surface for improved pedestri an head contact characteri st i c s .

CONCLUS I ONS

For pedestri ans i n th i s sampl e struck by the fronts of cars or l i ght goods vehi c l e s the fol l owi ng conc l u s i ons can be made .

1 . Approxi mate ly two thi rds of the vehi c l e s were brak i ng at impact . 2 . Leg i nj ur ies were the second most frequent non-mi nor i njury sustai ned . 3 . The majori ty ( 88% ) of the non-mi nor l eg i njur ies were fracture s . 4 . V i rtua l ly a l l ( 99% ) o f the non-mi nor l eg i njuries were caused by veh i c l e

contact . 5 . The bumper was respon s i b l e for 55% of the vehi c l e contact non-mi nor

l eg i njur ies and the front structure above the bumper for a further 36% . 6 . The severi ty of the pe l v i c and l eg i nj ur ies resul ti ng from contact wi th

the vehi c l e front structure i s dependent on the impact speed of the v.ehi c l e and the age of the pedestri a n . E l derly pedestri ans bei ng more suscepti b l e to susta i n i ng fractures for a g i ven impact speed .

7 . The l ocation of the bumper contact fractures i s i nfl uenced by the height of the bumper wi th respect to the pedestri a n . �1-

8 . Nearl y a l l ( 92%) the knee i njuries were caused by bumpers l ocated at a rel ati ve bumper height of 0 . 26-0 . 33 . I n absol ute terms th i s corresponds to a hei gh t range of 42-53cms taki ng 1 . 6m a s the average pedestrian hei ght .

9 . One quarter o f a l l veh i c les i n the sampl e for whi ch the bumper was located at 50-54cms above the ground caused a knee i nj ury to the struck pedestrian

1 0 . Loweri ng the pos i tion of the bumper appears to reduce the l i kel i hood of a fracture resu l ti ng from bumper contact .

1 1 . lnjuries to the ankl e can resu l t from contact wi th bumpers l ocated at a rel ati ve bumper hei ght of 0 . 1 6-0 . 20 and appear to be assoc i ated wi th h i gh speed contacts .

1 2 . Decreas i ng bumper l ead i s as soci ated with a decreased i nc i dence of bumper contact fractures and an i ncreased i nci dence of l eadi ng edge contact fractures .

1 3 . The el derly are part i cu l arly suscepti b l e to pel vic fractures . 1 4 . A l l the cases i n whi ch there was an acetabul um fracture i nvol ved

e l derly adul ts struck by vehi c le s for wh ich the l eadi ng edge was l ocated at a rel at ive height of 0 . 45 -0 . 51 and wh ich had short bumper l eads .

1 5 . E l imi nati on of non-mi nor pel v ic and l eg i njuries caused by vehi c l e contact by sui tab l e des i gn of the veh i c l e front structure wou l d resu l t i n a s i gni f icant reducti on i n the number of pedestri ans serious ly i njured .

ACKNOWLEDGEMENTS

F i nanc i al support for thi s study was provi ded by the Transport and Road Research Laboratory . Any v i ews expressed i n th i s paper are not necessari l y those of the Transport and Road Research Laboratory or any other part of the Department of the Envi ronment .

REFERENCES

1 . MACKAY , G . M . and de FONSEKA , C . P . Some a spects of traffic i njury i n urban road acGi dents . Proc . l l th Stapp Car Crash Conference . Paper 67091 0 . SAE . New York . 1 967 .

2 . McLEAN , A . J . a nd MACKAY , G . M . The exterior col l i s i o n . Proc . 1 970 I nt . Auto . Safety Conf . Compend i um . Paper 700434 . SAE . New York . 1 97 0 .

3 . KOLBUSZEWSKI , J . , BLA I R , I . , MACKAY , G . M . , CLAYTON , A . B . and de FONSEKA, C . P . Causes and effects of road acci dents . Dep t . of Transportat ion and Env i ron­mental P l anni ng , Univers i ty of B i rmi ngham . Departmenta l Report No . 3 3 . 1 96 9 .

4 . ASHTON , S . J . , PEDDER , J . B . and MACKAY , G . M . Pedestrian i njuries and the car exteri or . I n t . Auto . Eng . Congress . Detroi t . March 1 977 . Paper 770092 . SAE . New York . 1 977 .

5 . ASHTON , S . J . , HAYES , H . R . M . and MACKAY , G . M . Proc . I n t . Meeti ng B i omechani c s of Trauma to Lyon 1 974 .

Chi l d pedestri an i njuri es . Chi l dren . Lyon 1 974 . I RCOB I .

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6 . BACON , D . G . C . a nd W I LSON , M . R . Bumper characteri sti cs for improved pedes ­trian safety . Proc 20th Stapp Car Crash Conference . Paper 76081 2 . SAE . New York . 1 976 .

7 . J EHU , V . J . and PEARSON , L . C . The trajectories of pedes tri an dummies struck by cars of conventional and mod i fi ed frontal des i g n s . Transport and Road Research Laboratory Report No . 7 1 8 . TRRL . Crowthorne . 1 976 .

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APPENDIX l ANnE INJURIES SUS'l'AINED BY PEDESTRIANS STRUCK BY nm P'RONTS OF CARS AND LIGHT GOODS VEBICLES

CASE PEDESTRIAN !lUMPER HEIGRT IMPACT 'IEBICLE ROAD DESCRIPTION OF ANlCLE NUMBER :.11.11. AGE ABSOLU'it. RELATIVE SPEED BRAKING SURFACE AND OTHER LE.G INJURIES

157 M 74 28cm 0 . 1 7 4l-60km/h Sk�dding Dry Pressure marks to both ankles ; after Closed fr•cture right ankle.

Impact

190 M 81 28cm 0 . 1 7 41-SOkm/h Skidding Dry Extensive bruis ing inner aspect of at left ank l e ; Fracture right ankle

Impac t vith tearing of medial Ligaments ; Fracture upper third left tibia & fibula.

254 F 65 28cm 0 . 1 8 46-5Skm/h Skidding Damp Co111pound fracture left ankle after

Impact

APPENDIX 2 KN!E INJURIES SUSTAINED BY PEDESTRIANS STRUCK BY TBE FRONTS OF CAltS ARD LIGHT GOODS VERICLES

CASE PEDE�M!TAIJ BUHPER HEIGRT IMPACT VEHICLE . ROAD DE SCRIPT ION OF KNEE NUMBER SEX AGE ABSOLUTE RELATIVE SPEED BRAKING SURFACE AND OTHER LEG INJURIES

18 M 34 Slcm 0 . 30 26-30km/h Braking Wet Supracondylar fracture eo the at lefe femur .

Impact '

22 F 55 SO cm 0 . 31 26-30km/h Skidding Damp Fracture of ehe right tibial ae plateau.

Impact

100 F 73 43cm 0 . 29 ll-25km/h Braking Dry lOcm laceraeion to right knee ae overlying a crack fracture eo

Impac t tbe patella.

109 M 29 4Scm 0 . 26 > S lk:m/h Probably Dry Large bruise eo ehe left knee ; none Rupture of tbe ligaments in

botb knees.

167 F 62 38cm 0 . 26 Sl-60k:m/h Bra.king Dry Subluxed left knee wich ineernal after tearing of cruciate ligaments ;

Impact Bilateral fractures boeh tibiae and fibulae wich overlying lacerations.

183 M 9 SO cm 0 . 37 21-30k:m/h Braking Dry Fracture of tbe lef t tibial at plateau.

Impact

1 9 1 M 12 40cm 0 . 26 31-4Skm/h Not Dry Fracture to lef t anterior cib ial Known spine.

1 9 7 F 75 45cm 0.28 4 1-SSkm/h Bra.king Dry Supracondylar fracture to ehe . after rigbt femur ; Laceration to left

Impact lower leg and hip; Subtopical fracture to tbe left femur.

260 M 14 SO cm 0 . 31 31-40km/h Skidding Dry Displaced supracondylar fracture after rigbt femur . laceration eo rigbt

Impact knee; Displaced fraceure mid-sbaft left femur wich overlying l'aceration.

279 F 1 1 44cm 0 . 31 ll-30km/h Braking Dry Undisplaced fracture lower part at of rigbt patella.

Impact

299 F 72 SO cm 0 . 33 Sl-60km/h S�idding Dry Fracture lef t tibial head at invo lvi?g knee joint; Fracture

Impact m.id-shaft right femur .

320 F 66 48cm 0 . 30 46-55km/h Skidding Dry Supracondylar fracture left after femur .

Impact

330 F 16 54cm 0 . 33 66-7Skm/b Not Dry Fracture lower end right femur, Known fracture dislocation right knee ,

compound fracture right tibia and fibula

( 305 ) F 49 42cm 0 . 26 21-35k!W h Bra.king Dry Compresaion fracture to the after lateral condyle of ehe left '

Impact tibia wich haemoartherosis

APPENDIX 3 ACETABULUM FRACTURES SUSTAINED BY PEDESTRIANS STRUCK BY THE FR.ONTS OF CARS AND LIGHT GOODS VEBICLES

CASE PEDESTRIAN LEADING EDGE llEIGHT BUMPER IMPACT VEHICLE DESCRIPTION OF HIP AND NUMBER SEX AGE ABSOLUTE RELATIVE LEAD ANGLE SPEED BRAKING OTHER PELVIC AND LEG INJURIES

72 F 6 7 74cm 0.50 82° 41-45km/b Skidding Frac'ture right acetabulum with at elight dieplacement; Central

Impact dislocation. right hip;

Raad Dry Fracture left & right inferior pubic rami .

89 M 80 72cm 0.45 7 8u 31-45km/b Braking Fracture laft acetabulum;

at Dislocation left hip ; Fracture Impact left ilium, fracture left

Road Dry inferior pubic ramus ; Fracture upper third lef t tibia & fibula.

199 F 64 74cm 0.49 84° 31-40km/b Skidding ' S tove in' pelvis rigbt side at with central dis location right

Impact hip.

Road Damp

227 F 6.2 82cm 0.51 78° 11-20\cm/b Skidding ' Stove in' pelvis rigbt side at witb severe displacement of

Impact bead of femur through floor o f

Road Damp acetabulum.

320 F 66 74cm 0 . 4 6 82° 46-55km/b Skidding Fracture right acetabulum, after central dislocation right hip

Impact joint; Supracondylar fracture

Road Dry left femur.

(385) F 6 2 75cm 0 . 4 7 7 70 31-40km/b Skidding Fracture roof of right

after acetabulum; Couminuted Impact fracture inferior & superior

Road Dey right pubic rami ; Comminuted fract"""e left tibia & fibula,

S/