Evidence such as damage, principle direction of force, hair, andblood speaks volumes about how an accident occurred. Effectivelyutilizing this information can help settle a claim accurately andfairly. But where should an adjuster begin when reconstructing anauto accident in order to draw appropriate conclusions?

Snap to It

Usually, a vehicle involved in an accident will be moved to asalvage yard, so this is where the inspection begins. Beforeinspecting the vehicle, however, make sure that all of theappropriate approvals are obtained as well as special approval ifyou intend on removing any parts from the vehicle for analysis.Weather is crucial if subtle evidence is to be maintained, such asdust marks, blood, hair, and skin transfers. It is advisable tohave the subject vehicle covered until you can perform yourinspection if it is going to be stored outside. The vehicleinspection is a good example of documenting evidence through astill camera and video camera. If taking video, there should be nosound on the tape; it should strictly document the evidence withoutany description or narration.

Photographs, if shot properly, can be used to determine depth ofcrush-through, a process known as photogrammetry. This process iswidely accepted but the technique for performing the calculationscorrectly is not widely known. Photogrammetry can be simple or verycomplicated and depends on the information that is needed to beobtained from the photograph. To begin, the still camera must havea fixed-focus rectilinear lens to photograph the side of thevehicle and must be situated at right angles to the side whendetermining crushed depth from the front of a vehicle. According toJohn Daily's Fundamentals of Accident Reconstruction, the lensshould be level and at the height of the center of the mass of thevehicle pointing toward the center of the automobile. The processis a simple mathematical scaling ratio calculation that involvesmultiplying a known unit of measurement in the photograph with aknown unit of measurement of the subject part, which is thenmultiplied by the ratio to obtain the life-size dimensions.

Photographs documenting the principal direction of force foreach vehicle are crucial to the understanding of the dynamics ofthe before-and-after paths of the vehicles. It is also an importantelement in determining the kinematics of the vehicle occupants andeventually the biomechanics and mechanism of injury. Besides largecrush, very subtle evidence, such as striations and painttransfers, should be included in your pictorial documentation.Detailing evidence of seatbelt use is crucial when analyzing andinvestigating an accident involving specific types of injuries. Allsides of the vehicle should be photographed at an acute and linearposition to the plane. Overhead photographic documentation can bedone by mounting the camera on a PVC pole with a mechanism to snapthe shutter. This overhead method of photography can be crucial ifyou need to determine the speed of a vehicle at impact from thedamage incurred (crush information).

The Outside Counts

Anytime vehicle damage is the predominate method in analyzing acollision, the properties of metal parts must be considered.Stiffness of metals relating to vehicle collisions are anindication of the resistance of a metal at a given angle topermanent deformation or crush. Restitution of a metal is therebound relating to the angle and force of impact. Both of thesevalues are necessary if an accurate and unbiased investigation andreconstruction are to be performed. Paint transfers, which occurwhen two surfaces of different color are forced together, creatingfriction that temporarily melts the paint, can be very subtle orvery obvious depending upon the angle and speed at collision.

Another important area relating to vehicle damage includes thematching of roadway scraps, gouges, and scratches with theundercarriage of the vehicle. Vehicles can leave the roadway andstrike roadway signs, traffic-signal posts, wooden polls, trees, orculverts. Each one of these impacts usually leaves a distinctivedamage profile that aids in identifying the dynamics of thevehicles. The type of damage concerned with absorbing energy andspeed determination comes from contact damage as opposed to induceddamage. Contact damage is the damage directly caused from contactbetween two objects. Induced damage is a result of contact damage,such as the bottom of a windshield breaking from the hood beingpushed rearward.

Wheel rims and tires can reveal important clues as to how anaccident occurred, too. Tires can blowout slowly or quicklydepending upon the object they strike. Wheel rims can be bent fromimpacts with curbs, potholes, or other objects. When tires andwheels are damaged, a thorough investigation should reveal thecause and also the effect on the vehicle itself. For example, if avehicle leaves the roadway and the driver attempts to recover, theinside edge of the tire usually will have scrape marks if thedrop-off of the pavement is approximately four inches or greater.Fluid leaks on the roadway can tell the story of initial andpost-impact travel as well as the point of rest. However, be awarethat fluid naturally seeks the lowest point of the roadway, so donot assume that pooling fluids indicate the final point ofrest.

Vehicle lighting can be crucial when investigating left or rightturning vehicles and nighttime accidents. Headlights or turnsignals that have one or two filaments can be used to determinewhat is called cold or hot shock. If a lamp is illuminated, thefilaments can reach temperatures as high as 2300 degreesFahrenheit. If a severe force was applied in this state, the lawsof physics would dictate that the filaments would move or bend inthe direction of this force. Additionally, according to RudolfLimpert, author of Motor Vehicle Accident Reconstruction and CauseAnalysis, if the glass headlight bulb breaks, the filaments willshow signs of oxidation after having come into contact with air.When inspecting a vehicle, it is imperative that the lights are notturned on, since doing so will destroy this type of evidence. Ifyou decide to move the lamps, special documentation and orientationup or down must be maintained. It is possible that, if the glass isbroken when the filament is hot, glass pieces will melt and adhereto the filament wires. It should be noted that not all lamps andbulbs have this type of filament.

Useful information also can be obtained by inspecting bumpersand their accompanying structures. Bumpers have thresholds that,once surpassed, result in permanent damage. All bumper systems arenot equal and consequently have different damage thresholds. Damagethresholds are much less for barrier crash tests than inreal-world, vehicle-to-vehicle impacts. The reason for this is thatin barrier impacts, all of the energy is used to damage thecrash-test vehicle, while in real-world situations, both vehiclesabsorb energy from the impact. The structures of bumpers includebumper bars, bumper isolators, frame brackets, and Styrofoamabsorbers. Bumper isolators are small shock absorbers mountedhorizontally behind the bumper and are intended to take in theenergy from impacts before it reaches the frame of the vehicle. Byanalyzing the distance of movement or collapse of the isolator, onecan compare results with tests to determine an approximate value ofenergy absorbed. With this information, an approximate impact speedcan be determined. This procedure must be done for both vehicles;if only one vehicle is inspected, only half of the evidence hasbeen analyzed. Styrofoam bumpers are made to be used one time,since these types of bumpers terminally deform when absorbingenergy whereas the isolator will usually return to its undamagedposition, if the impact has not surpassed the isolator'sthreshold.

Take a Look Inside

The interior of a vehicle is just as important to inspect andanalyze as the exterior. Usually, interior evidence consists ofoccupant movements and mechanisms of injury. Occupants alwaystravel towards the impact; if there was a forward impact, forexample, all occupants would move towards the front. If the impactis offset, such as 30 degrees from the centerline of the vehicle,the occupants would move towards this 30-degree impact. Windshieldscan become cracked from various objects, most typically fromunbelted individuals. Windshields are now made so that they willnot splinter and break in many pieces, which can seriously injureoccupants. They are now designed to shatter and usually stay in onepiece. Side windows are not designed the same way; shattered glassfrom these can indicate whether the force came from within thevehicle or outside of the vehicle.

Instrument panels or dashboards used to be very dangerous andproduced more injuries at lower speeds than today's designs do.Dashboards and steering wheels today are padded and airbags havebeen designed to prevent the occupant from reaching them. Seatbeltscan be analyzed to rule out use or nonuse by the occupant.Seatbelts that have been used usually show marks on the latchingsystem and stretching or loading of the belt fabric, according toR.W. Rivers' Seatbelt & Air Bag Systems Manual. Injuriescompatible with extreme forward displacement are usually caused bynot using seatbelts.

Lower areas, such as underneath the dashboards, are anothersource of serious injuries for unbelted individuals. Typicalinjuries include fracture of the tibia, fibula, femur, or hip. Aninvestigation of the area is necessary to match up the injuries tothe occupant. This type of investigation is most useful when noneof the occupants will admit to driving and the possibility ofalcohol or drugs is involved. Hair, blood, skin tissue, and injurypatterns all tell a story as to the seated position of occupants.An inspection of the vehicle should include measurements from thesuspected seating position to the dashboard and steering wheel.This information is necessary to assess seatbelt usage.

With the onset of airbags, injuries have been reduced even moreso when combined with seatbelts, but they also can reduce injuriesif used alone. Deployment of airbags can give an indication of theDelta-V or severity of the impact. Airbags can deploy at variousDelta-V speeds, usually over 14 mph, according to J.C. Marsh IV'spaper for the Society of Automotive Engineers entitled,“Supplemental Airbag Systems: Consumer Education and Experience.”Impacts between eight and 14 mph may cause airbags to deploy,though. The direction of impact for proper deployment of theairbags is usually within a range of 30 degrees of either side ofthe vehicle's centerline.

Seat cushions and seatbacks as well as headrests also are veryimportant when inspecting a vehicle. A properly positioned headrestcan drastically reduce injuries such as whiplash. Whiplash occurswhen a rear-end impact forces the torso of the occupant forwardwhile the head and neck, still wanting to occupy the same space(inertia), remain stationary. The seatback also plays an importantpart because of energy absorption as the torso is forced into theseatback and the stored energy is released, propelling the torso ofthe occupant forward. This force, at times, can be faster than thevehicle itself because of a slingshot effect.

Another area that is important to inspect for side impacts isthe glass fragments from the side windows. Matching up occupantinjuries to the side door and the center console for a right sideimpact where the driver may slip out of the shoulder portion of theseatbelt and contact the center console or gearshift should also bedone.

Reconstructing vehicle accidents is an important part ofproperly adjusting an auto claim and can help determine properliability. By conducting a comprehensive and scientificinvestigation of the accident scene and the vehicles involved, moreoften than not, an adjuster will be able to effectively make hiscase as to what happened.

Dennis Andrews is principal of Accident & SafetyConsultants. He can be reached at 856-596-6903.