real world car crash investigations – a new approach

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Real world car crash investigations – A new approachM Lindquist , A Hall & U Björnstiga Emergency and Disaster Medical Centre, Department of Surgery, Umeå University,SE-90185 Umeå Saab Automobile AB, Trollhättan SE-46180b Enginuity Services International, Woking, England, GU 22 ODY, (www.enginuity-services.com)c Emergency and Disaster Medical Centre, Department of Surgery, Umeå University,SE-90185 UmeåPublished online: 08 Jul 2010.

To cite this article: M Lindquist , A Hall & U Björnstig (2003) Real world car crash investigations – A new approach,International Journal of Crashworthiness, 8:4, 375-384, DOI: 10.1533/ijcr.2003.0245

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© Woodhead Publishing Ltd 0245 375 IJCrash 2003 Vol. 8 No. 4 pp. 375–384

Corresponding Author:M Lindquist, Saab Automobile AB and Emergency and Disaster MedicalCentre, Dept of Surgery, Umeå University, SAAB Automobile AB,A17-1 TVACB, SE-46180, Trollhättan, SwedenTel +46 520 86740 Fax +46 520 78310Email: [email protected]

INTRODUCTION

The purpose of this paper is to present a new, more detailed,crash research methodology to provide a more viable long-term real world crash statistics database. A more detailedand regulated crash database would allow a greaterunderstanding of the causes of real world injuries. Thispaper presents both historical and current thinking withinthe automotive industry regarding crashworthinessperformance. The premise of the new methodology isthat “a sound understanding of real world crash dynamics”leads to better theories upon which future development/assessment protocols should be based.

The underlying concept that this paper presents is basedon improving our understanding of real world crashes (in

terms of cause and effect of sustained injuries). Thusproviding necessary data, to better focus the futuredevelopment of effective comparative test methodologies.It is the development of new test methods that will guidethe research of future occupant restraints/protectionsystems.

It should be noted that this paper focuses on frontalimpact scenarios only; this is intentional so as not to confusethe reader with the special considerations necessary withrespect to both side and rear impacts.

HISTORICAL BACKGROUND

The first initiative to examine frontal crash performanceof cars was taken in the USA where the US-NCAP (NewCar Assessment Program) [1] was launched in the latenineteen seventies. In this crash test the subject car wascrashed perpendicular to a flat, rigid barrier, with an impactvelocity of 35 mph (56 kph), see Figure 1. The purpose ofthis program has been to provide consumers withinformation to compare perceived occupant protectionthat each car model line provides. Even today this program

Real world car crash investigations –A new approach

M Lindquist*, A Hall** and U Björnstig****Emergency and Disaster Medical Centre, Department of Surgery, Umeå University, SE-90185 Umeå SaabAutomobile AB, Trollhättan SE-46180** Enginuity Services International, Woking, England, GU 22 ODY, (www.enginuity-services.com)*** Emergency and Disaster Medical Centre, Department of Surgery, Umeå University, SE-90185 Umeå

Abstract: By actively researching real world crashes it has become apparent that existing methodologiesfor recording car deformation for severe injuries and fatalities are limiting our ability to effectivelyinterpret the cause and effect relationship to the sustained injuries. This paper provides a historicalview of crashworthiness development, explaining current data collection methods for analysing realworld crashes before presenting a new approach in real world crash data collection. The new methodologyaims to substantially improve our understanding and analysis of the cause and effect of injuries thatare seen in everyday crashes. This improved understanding is achieved by examining the behaviourof the structural elements in the car body during a crash. A generic car model has been developed,consisting of beams, joints and plate areas, which is used during car inspection. The main goal is clearidentification of the load path usage during the crash.

It is identified that there is a need for better understanding of real world crashes so as to be ableto provide the automotive industry with more accurate statistical information for different crashtypes. The authors note that accurate statistical information is required in order to guide futurechanges in the crashworthiness testing protocols to be effective in reducing the crash dynamics thatare the cause of real world injuries.

This paper singularly presents a new methodology, whilst referring to current ongoing work usingthis approach.

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M Lindquist, A Hall and U Björnstig

IJCrash 2003 Vol. 8 No. 4 376 0245 © Woodhead Publishing Ltd

is still run, with the results published on the Internet forconsumers to review. Following the initiation of thisprogram, the USA implemented the philosophy of thistest method for new car designs to comply with. Thisresulted in a reduced impact velocity to 30 mph (48 kph),as a legal requirement known as FMVSS 208 (FederalMotor Vehicle Safety Standard). Over time the USGovernment has implemented progressive changes tolegislation in the attempt to improve car occupantprotection.

The test methods currently used were based upon thedevelopment of a very simplified representation of a humanoccupant. These artificial occupants (more commonlyknown as “Crash Test Dummies”) were developed fromcadaver testing, where human body limits to acceleration,force and displacement were established for different bodyregions during a controlled crash event. The current humanlike crash test dummies are more commonly known as theHybrid III dummy series. The main body regions of theHybrid III (the head, chest and pelvis) have accelerationmeasurement devices, where as the femur measurecompressive loads, and the chest can also measurecompressive displacement of the sternum. Since theintroduction of the Hybrid III in the early seventies, therehave been several additions to the available instrumentation(in the areas of neck, lumber spine and lower leg forceand moment measurement).

Due to crash performance being primarily judged bydummy responses, it is essential that the vehicle frontstructure can provide a controlled ride-down efficiency.The best way to achieve this is to have an even crush forceduring the deformation of the entire front structure length,in addition to increasing the deformation length itself.

There is no doubt that these crash tests forced theautomotive industry to focus their efforts to substantiallyimprove frontal crash performance. Additionally it shouldbe noted that although the 3-point seat belt ispredominantly the primary restraint to the occupants,significant changes have been made since it was introduced.It is now common for manufacturers’ to combine pre-tensioner and load limiting devices to be used inconjunction with the basic 3-point belt design. Similarly,due to the change in emphasis in the USA from unbeltedoccupants to belted occupants, airbag technology has comea long way with the development of multi-stage inflatorsand airbag trigger switches to turn off the passenger airbag

due to the usage of either rear facing child seats in thepassenger seat, or even occupants seated too close for safeairbag deployment.

For some years, starting in 1990, the car magazine “AutoMotor und Sport” in Germany performed and publishedcrashworthiness information using an overlap of 50% ofthe impact barrier to the car [2]. This was the firstmainstream consumer crash test methodology in Europe.

In the early nineteen nineties European crash researchersbegan discussing the limitations of the USA testmethodology with respect to the full frontal impactapproach. European researchers presented real world crashdata, which suggested that a crash test with only a portionof the front of the impacting car striking a barrier wouldbe more representative of the European crash condition[3–4]. The investigation of occupant injuries indicatedthat the majority of serious injuries were due tocompartment collapse and intrusions. Auto manufacturersVolvo and Mercedes, as well as European researcherssupported this view [5–6]. Further to this researchershave observed that the deformations of the stiff longitudinalmembers were not in the same magnitude in real worldcrashes when compared with crash tests into rigid barriers[7]. In order to produce a representation of thesephenomena in a test environment some researchersproposed the use of a deformable barrier. In 1996 theTRL (Transport Research Laboratory) started a programof consumer crash testing in the UK, using an impactconfiguration of 64 kph to an offset deformable barrierwith a 40% overlap. This was soon adopted within Europeas the Euro-NCAP [8]. In 1998 a new crashworthinesslegislation using the same deformable barrier, but at alower speed (56 kph), came into effect. The test results ofthe Euro-NCAP are published with the same purpose asthat of the US-NCAP. In the USA the IIHS (InsuranceInstitute for Highway Safety) nowadays conducts someof their crash tests almost according to the Euro-NCAPtest protocol for consumer information [9].

It was not only the test configuration that wassignificantly different in the Euro-NCAP. The post-testcar assessment examined the occupant compartmentintegrity, particularly foot-well intrusion. In the Euro-NCAP assessment large deformation of the foot-well resultsin possible lower rating. Due to the new design criteriaoriginating from the Euro-NCAP, car manufacturers havebeen significantly challenged to reduce foot-well intrusion.It is primarily due to the new design criteria that acontradiction can be seen to exist between US-NCAPand Euro-NCAP. For a good US-NCAP performance aprolonged deformation distance is good, which in turnleads to a better ride-down efficiency, and lower dummyreadings. Where as for the same car, no foot-well intrusionis good for the Euro-NCAP, thus reducing the possibledeformation distance.

Today the general opinion is that the US-NCAP andEuro-NCAP tests compliment each other. With the moresevere crash pulse in the US-NCAP testing interior safety,

Figure 1 US-NCAP and FMVSS 208 test configuration.

Impact velocity

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Real world car crash investigations – A new approach

© Woodhead Publishing Ltd 0245 377 IJCrash 2003 Vol. 8 No. 4

whilst Euro-NCAP is a test of car structure andcompartment integrity.

FRONTAL CRASH COMPATIBILITY

With significant changes to car safety already showingbenefits through observed reductions in fatalities, the safetycommunity has shifted their focus toward the problem ofvehicle compatibility. This is mainly due to the largevariation in vehicle sizes and masses within the carfleet.

It is considered that if two cars are colliding thecompatibility, as defined by some authors, is thecrashworthiness of the impacted car, and the aggressivityof the impacting car. The term crashworthiness is oftenreferred to as being the self-protection or the ability ofthe car to protect their occupants in a crash [10–14]. Theaggressivity of a car is expressed in terms of the risk ofproducing injuries to the occupants in the other car involvedin the collision; otherwise referred to as partner protection.

Currently there are three major key factors that aregenerally considered to influence the compatibility duringvehicle-to-vehicle impacts [10–14]. A brief overview ofeach factor follows:

1 – Vehicle mass

Typically in crash scenarios, the vehicle mass isconsidered to be the active mass (i.e. the initial solidvehicle self mass that loads the structure). Active massdoes not include either occupant or luggage masseswhich are initially in free flight at the instant the carstarts to decelerate.By considering Newtonian physics it is obvious that aheavy (rigid) mass impacting a light (rigid) mass withopposing equal initial velocity will always result in ahigher deceleration in the lighter mass relative to theheavy mass. This is all well and good for rigid entities,but cars have a front-end stiffness. Some authors haveidentified mass as the largest factor to incompatibilitybetween vehicles in real life crashes [15–16]. However,other authors have argued against this conclusion as anisolated factor due to the influence of relative front-end stiffness and interior protection [13].

2 – Front-end stiffness

When a vehicle with a stiff frontal structure collideshead on with a vehicle with a weaker front structurethe main deformation will occur in the weaker structure.This will increase the risk of passenger compartmentdeformations in the weaker vehicle and thus increasethe risk of passenger injuries. There have been opinions,especially among automakers, which have presentedarguments that the offset barrier tests like Euro-NCAPhave forced the automakers of heavier vehicles tounnecessarily increase the frontal stiffness which willlead to a stiffness incompatibility with lighter vehicles.This view has been rejected by Nolan [17] who argues

that the offset barrier test increases the compartmentstiffness rather than the front-end stiffness.

3 – Geometrical differences

Geometry plays an important part in vehicle design,with exterior styled surfaces, and the more discreetstructure load paths typically restricted by vehiclepackaging constraints. These factors have resulted inlarge disparities between different vehicle classes withrespect to geometrical interaction during a car crash.It is currently an area of great discussion in the USAwhere the vehicle fleet has a high proportion of SUV’s(sport utility vehicles) and pickups. These obviouslyhave a great difference in both bumper and longitudinalheight in relation to a normal car. Such disparities areconsidered to be a cause for concern due to the over-ride effect (where an impacting SUVs’ bumper andlongitudinals fail to engage the main load bearinglongitudinals by over riding, similarly the impactedcar is considered to be in a condition of under-ride)[13,18].

By looking at the current legislation requirements, alongwith the more demanding consumer crash tests, it can beseen that the manufacturers have been encouraged toimprove the crashworthiness (or self-protection) in theirvehicles. This has led to the development of front structuresthat have good energy absorption abilities in these crashconfigurations, and has undoubtedly increased the safetymargins for the occupants and hence overall vehicle safety.However, an incompatibility condition occurs when thesevehicles impact with other vehicles or obstacles whicheither bottoms out the energy absorption capacity of thefront structure, or are directing the crash forces throughsecondary load paths (i.e. not through the primary crashstructure). One such crash configuration is that of thesmall overlap. A small overlap is considered to typicallyresult in minimal crash structure engagement during thecrash event. In essence the occupant cabin becomes thefirst substantial load path when such a crash configurationoccurs.

It can be concluded that the key in quantifying thevalidity of current crash testing, along with future protocoldevelopments, is to collect real world crash data moreappropriate to understand real world crash load pathsand the resulting occupant injuries. In the following sectionthe authors presents a new methodology to real worldcrash data collection and analysis in order to produce adetailed picture of the trends in crashworthiness towardsreal world occupant injuries.

METHODOLOGY – CRASH INVESTIGATION

Study of existing methods

The first step in the process of creating a vehicle inspectionprotocol was to study existing methods of crashinvestigation and/or deep study activities. There are few

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well-documented methods of crash investigations but somemethods could be studied in detail. The first is the NASS-CDS (National Automotive Sampling System-Crashworthiness Data System) that represents the methodused in the USA [19]. The second method studied is theresult of the STAIRS-project (Standardization of Accidentand Injury Registration Systems), which was a commonEU-project with the aim to standardize crash investigationsin Europe [20]. Other studied methods are the ones inuse in the UK, CCIS (Co-operative Crash Injury Study)and in Accident Research Unit Hannover in Germany[21–22]. Finally the methods used by the CIREN projectin the USA studied [23–24].

In these methods the most common method ofdescribing the extent of vehicle deformations is the SAEJ224 practice, Collision Deformation Classification (CDC)[25]. A brief description of this practice follows. The extentof deformation is described by a seven-character code.The first two characters indicate the PDF (PrincipalDirection of Force) acting on the subject vehicle. Principalforce is a vector considered to be resultant force; thedirection of this force vector is then designated by referenceto hours sectors on a clock face. The third characterdesignates the area of deformation and is most commonlycoded as a frontal, rear, side or top (roll-over) impact.The fourth and most important character in these mattersdesignates the specific lateral damage location or in thecase of frontal impacts the width of overlap in 33% steps.The deformation plan is shown in Figure 2 below.

If, for example, only the left one third of the front isdeformed then this is coded as “L”. If the whole front isdeformed then “D” is used and finally if the left twothirds is deformed then “Y” is used. The three remainingcharacters, character 5–7, in the CDC code designatevertical damage, type of damage distribution and the extentof damage.

In Germany, Otte additionally describes the frontaldeformation with a matrix covering the vehicle front [22].The vehicle examiner notes elements of the matrix whichare considered to be included in the deformation area.Other sources prefer to express the percent of frontalwide involved in the collision [26].

The sub-division of the front structure

A survey of modern car structure was carried out,identifying the “body-in-white” structure of models fromthe car manufacturers that are represented in the Europeanmarket. This was achieved by studying surveys and research

papers [27–28]. During this process it became obviousthat there is little variation in the fundamental constructionof vehicle body-in-whites between automakers. The carindustry of today is global and very few independent carmakers remains. A newly developed car structure is typicallyshared by several car models of one car manufacturinggroup with small stylized and structural modifications.Another explanation for this could be that all demandsfor the structure, including crash testing like US-NCAPand Euro-NCAP, makes the optimal solution limited. Inthis way it was possible to identify a generic car structurethat represents all car models studied. This includes currentmodels by BMW, Citroen, Fiat, Ford, Honda, Mazda,Mercedes, Nissan, Opel, Peugeot, Renault, Rover, Saab,Toyota, Volvo and the VW-group.

The generic car structure is constructed by using threedifferent basic elements; beams, joint connections andplate areas. A beam, commonly known as a structuralmember, typically has a closed section with a specific length.Examples of beams are the longitudinals, sills and b-pillars.These beams are connected to the structure by joints. Itis important to view these joints as separate constructionelements because during a crash a beam can be disorienteddue to joint failure causing large global deformations. Inthese cases the beam is generally undeformed and has notdissipated any energy. Examples of plate areas are thedash-panel in the engine compartment and the floor inthe passenger compartment.

Due to practical reasons the total structure is dividedinto regions. These are frontal, left side, right side, roofwith pillars, compartment floor and rear end. This divisionof the total structure makes the inspection of the crashedvehicle easier during the field investigation. Theconstruction of the frontal structure in the generic carmodel with these basic elements is presented inFigure 3.

Definition of load paths in frontal collisions

Load paths are typically defined as the parts of a vehiclethat are able to produce resistive forces during a crashevent. Within this project it was identified that there arenine load paths that can be reviewed easily post crash forsigns of loading. To support understanding of each ofthese load paths a schematic diagram was created, seeFigure 4.

So as not to bias the reader into thinking that particularload path sequences always occur, the schematic identifieseach load path starting from the left side of the vehicle,

Figure 2 Definition of the fourth and fifth CDC characters, specific lateral damage location and specific vertical or lateralarea.

D

Z

YC

L

R

L

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looking at each load path encountered as we move acrossthe vehicle to the right hand side.

A detailed description of each of the load paths definedin Figure 4 follows:

1 (9)[*] Direct loading of the left (right)[*] side structure.In this loading condition the hinge pillar, doorand B-pillar are directly loaded, mainly in thelongitudinal direction. When this load pathoccurs, the crash type is often referred as a “side-swipe” with small lateral deformations of theside structure being present. This crash type isclassified as a frontal collision with the sidestructure as the frontal resistive structure.

2 (8)[*] Direct loading of the left (right)[*] front wheel.In this loading condition the load is transmittedthrough the wheel to the lower part of the hingepillar, and the sill structure. In should be notedthat the initial loading of the wheel transmitsloads through the front suspension lower controlarm. However, sudden high loading of the lowercontrol arm typically results in the lower controlarm detaching (either partially or completely)from the sub-frame.

3 (7)[*] Direct loading of the left (right)[*] upper sidestructure (commonly known as the shot-gun).This load path transmits the forces to the upperpart of the hinge pillar and the adjoining dashpanel.

4 (6)[*] Direct loading of the left (right)[*] mainlongitudinal members. This load path transmitsthe forces to the lower part of the dash panel,compartment floor and side structure. The energyabsorption capabilities of the longitudinalsare an important factor with respect to thebehaviour of the total front structure duringbarrier testing.

5 Direct loading of the drive-train. This load pathoccurs after some initial front-end deformation.Following the initial loading of the drive-trainand a small amount of surrounding structuraldeformation (or following fracture of one or moreof the drive-train mounts), the forces aretransmitted into the dash panel which transmitsthe forces to the plenum area, tunnel and hingepillars. It should be noted that this load pathproduces the single largest source of resistiveforces during barrier crash tests. This is due to

Figure 3 Description of main parts in the generic frontal structure.

5 67

8

9

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4

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1

No. Description Note

1 Bumper Beam

2 Longitudinal (lower frontal beam) Beam

3 Shock tower (spring strut)

4 Shotgun (upper frontal beam) Beam

5 Dash panel (fire wall) Plate Area

6 A-pillar (upper a-pillar) Beams

7 Hinge pillar (lower a-pillar) Beams

8 Front sill Beams

9 Drive-train

Figure 4 Description of identified load paths acting on the generic frontal structure.

LoadPath No.

Description

1Direct load to left side structure (hinge pillar, door, b-pillar)

2Load on left front wheel transmitted to front sill andhinge pillar

3Load on left shot gun beam/shock tower transmittedto hinge pillar and side structure

4Load on left longitudinal transmitted to compartmentfloor and dash panel/hinge pillar area.

5Load on drive-train transmitted to the dash panel andcompartment floor.

6Load on right longitudinal transmitted to compartmentfloor and dash panel/hinge pillar area.

7Load on right shot gun beam/shock tower transmittedto hinge pillar and side structure

8Load on right front wheel transmitted to front sill andhinge pillar

9Direct load to right side structure (hinge pillar, door,b-pillar)

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the large contact area and the incompressiblenature of the drive-train.

Note [*]: So as not to be repetitive with descriptions ofsymmetric loading conditions, the right side load path is addedin the left side description using bold italics for clarity.

In barrier crash testing such as Euro-NCAP and US-NCAP the load paths used depend on the barrier size andoverlap (Figure 5). The barrier used in US-NCAP crashtests covers the whole frontal structure in both the widthand height. For this crash test the majority of the loadpaths identified in Figure 4 are used, the exceptions beingload path 1 and 9. The barrier does not put direct loads tothe side structures. In Euro-NCAP testing the barrieroverlaps 40 % of the frontal structure on the driver side.In this crash test the barrier closest to the car centrelineindirectly interacts with the drive-train (on most cars)[29]. Thus the load paths used are 2 to 5 and 5 to 8, forLH and RH drive cars respectively.

In many of referred papers the crash pulse in thesebarrier crashes are described as the schematic crash pulsein Figure 6 below. In the beginning of the crash only thelongitudinals are producing a resistive force that forcesthe car to decelerate with an average acceleration a1. Whenthe deformation reaches the drive-train (engine) and whichthen strikes the dash panel this load path produces a resistiveforce that forces the car to decelerate with an averageacceleration a2. This implicates that the most importantload paths used in barrier crash testing are left and rightlongitudinals and drive-train to dash panel. Theacceleration a2 is by magnitude larger than a1 that implicatesthat drive-train to fire wall is the largest load path. InEuro-NCAP crash testing only one longitudinal producesthe acceleration a1 which causes this average accelerationto be smaller when compared to full barrier testing.

In conclusion the validity of current barrier crash testmethods depends on the extent to which these load paths(longitudinals and drive-train) are engaged in real worldcrashes.

A new methodology for crash data collection

In order to simplify the data collection process (vehicleinspection) the body-in-white structure is divided intosix regions. Front end, left side, right side, roof with pillars,

floor and rear end structure. Five of the six regions weredefined based upon deformation zones which occur withintypical crash configurations (Front, side, rear and rollovers).The sixth region (the floor area) is chosen as a separatearea on to which the occupants seat structures are typicallymounted. These regions are separated into beams andplate areas (see Figures 7–11). Each beam is connected tothe rest of the structure by joints that are considered tobe a separate construction entity.

The generic car model consists of 24 beams with 34joints and 4 plate areas. In most crashes only a few ofthese construction elements are deformed. Within thevehicle inspection protocol it is possible to add remarksto each of the construction elements. The types of remarktypically made are presented in Table 1 below.

Within the vehicle inspection protocol the generic carmodel is presented graphically. When adding a remarkfor an element, both the remark type according to Table 1and the position of the remark on beam or plate area arerecorded. Each construction element can have either oneor several remarks.

Vehicle deformation measurements are also added tothe vehicle inspection protocol. In addition to the totalvehicle deformation, the deformation of specific structuralmembers is recorded. These measurements were selectedin order to be able to identify load paths used in the collision.The measurements are taken with a tape measure withthe intention of being reached easily during the fieldinspection. Measurements for frontal collisions are shown

BarrierBarrier

Figure 5 Barrier coverage in barrier testing according to US-NCAP (left) and Euro-NCAP (right).

a1

a2

Longitudinaldeformation

Engine to firewall deformation

Time

Velocity

Figure 6 Schematic crash pulse in barrier crash testing.

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in Figure 12 below. Additionally foot-well deformationsin accordance with the Euro-NCAP test protocol are takenalong with roof deformations.

Another important aspect of vehicle deformation infrontal collisions is the stack-up effect within the enginecompartment. A secondary load path begins when near

incompressible components (for example battery, absmodules and engine mount etc.) are compressed together.The inspection protocol also includes possibilities forremarks of this type of load path usage.

For a full frontal impact, the most important stack-upload path is the drive-train to dash panel. The presence

Figure 7 Description of frontal end structure.

7

1 2 3

456

No. Description Type

1 Right A-pillar Beam

2 Right B-pillar Beam

3 Right C-pillar Beam

4 Left C-pillar Beam

5 Left B-pillar Beam

6 Left A-pillar Beam

7 Roof Plate Area

1

2

Tunnel

Compartmentfloor 3 Rear seat

Front


1 Left seat beam Beam

2 Right seat beam Beam

3 Floor Plate Area

Figure 8 Description of side structure.

Figure 9 Description of roof structure with pillars.

Figure 10 Description of floor structure.

8

7

6

5

43

21


1 Left hinge pillar (lower a-pillar) Beam

2 Left shot gun (upper front beam) Beam

3 Left longitudinal Beam

4 Bumper Beam

5 Right longitudinal Beam

6 Right shot gun (upper front member) Beam

7 Right hinge pillar (lower a-pillar) Beam

8 Dash panel Plate Area

45

6

7

12

3


1 Rear sill Beam

2 Front sill Beam

3 Hinge pillar Beam

4 A-pillar Beam

5 B-pillar Beam

6 C-pillar Beam

7 Rear wheelhouse (dog leg structure) Beam

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and magnitude of this load path can be detected in threeways, traces of direct loads on the drive-train (mostcommonly radiator deformations), disconnections byfracture of engine mounts and engine deformations ofdash panel. These three aspects of drive-train involvementare also included within the inspection protocol.

Additionally the sub-frame structure is recorded alongwith the drive-train.

The information recorded within this inspectionprotocol makes it possible to identify the load paths thatoccurred during the crash event.

DISCUSSION

The current test protocols have all been developed frominterpretations of statistical crash data. Over the last tenyears there has been a substantial change in thecrashworthiness development of cars due to both legislativeand consumer crash testing. Automakers go to great lengthsto optimise their structural designs for crashworthiness.However, with the current research area of compatibilityproposed as the next step in crashworthiness (pedestriantesting is considered separate from normalcrashworthiness), it is necessary to ensure that future testingprotocols benefit car designs for reducing real worldfatalities and severe injuries. This is the current dilemmasince real world crash databases provide the statistics upon

Spare wheelrecess

3

1Left rear sill

4

2Right rear sill


1 Left rear beam Beam

2 Right rear beam Beam

3 Rear bumper Beam

4 Rear floor Plate Area

Figure 11 Description of rear structure.

Table 1 Possible remarks on each element type

Observed Description Element typesdamage affected

Buckling Deformed in length Beam, plate area(due to axial loading)

Folds Deformed due to bending Beam, plate areaDent Section deformation, no Beam, plate area,

deformation in length jointPlate tearing Tearing of material Beam, plate are,

jointWeld tearing Tearing of welding Beam, plate area,

connections Beam, plate area,joint

Figure 12 Description of frontal collisions measurements in vehicle inspection protocol.

1 3

42

8

7

6

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11

10

9

No. Description

1 Right longitudinal front end – shock tower centre

2 Left longitudinal front end – shock tower centre

3 Right shock tower centre – wind shield line

4 Left shock tower centre – wind shield line

5 Left front wheel centre – rear wheel centre

6 Door opening deformation, sill level

7 Door opening deformation, lock level

8 Door opening deformation, waist level

9 Left bumper (at longitudinal joint) – rear axle

10 Bumper centre – rear axle

11 Right bumper (at longitudinal joint) – rear axle

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which future changes in crashworthiness development willbe based. The current real world crash data collectionpractices are both old and simplistic in concept. It shouldbe noted that to date, the statistical interpretation of existingdata has proved to be an invaluable guidance in directingcrashworthiness development. However limitations willexist into the usefulness of interpreting existing data whenfatalities tend to be special load cases. It is because of thespecial load cases identified throughout this paper that anew methodology for data collection is being proposed.

CONCLUSIONS

Current methods of describing vehicle deformations foraccurate statistical analysis of real world accidents arelimited in their data collection approaches. The limitationsof these relatively old data collection techniquessubstantially reduce the ability of crash researchers toidentify key trends, regarding the actual usage of vehiclestructures during crash events. To overcome the currentlimitations a new post crash data collection methodologyhas been developed, as part of a larger real world accidentstudy. The key points of the new methodology addressconcerns from researchers regarding the rather vagueinformation that is collected regarding structural damageduring a crash event that is part of current methodologies.The new methodology provides a detailed recording systemthat allows for a significant improvement in recorded crashdamage. The level of detail attained during the post crashreview provides significant advantages for data analysis ofreal world accident trends.

The development of a new methodology was the firststage of a real world crash investigation into theunderstanding the causation of occupant injuries resultingfrom crash events. The analysis of both the structuraldamage and the occupant injury trends are publishedseparately, in order that a clear and focussed review of theresults is presented.

FURTHER WORK

This method of crash investigation is in use in collectingdata from real world crashes by two sources. The firstsource is fatal crashes in Sweden and the second source iscrashes were the occupants have been admitted toemergency care at the University Hospital in Umeå,Sweden.

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real world car crash investigations – a new approach

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