A Desk Top Review

The red Fiat and the red Ranger collided. The insured and claimant differed greatly in their stories as to what occurred. The vehicle damage was repaired, and there was no police report. Could we look at photos and tell what really happened? In this case, yes. GEI has a document review program designed for low speed automotive cases like this one, where a physical inspection is impractical or impossible. Typically we are asked:

· Which version of the accident is most probable?

· Could these vehicles have been involved in this accident?

· Is the damage to the vehicles commensurate with this accident?

· What were the speeds, g-forces, and probability for injury in this accident?

We review all of the relevant available documents and form an expert opinion, based upon the supplied documentation. In this case, the insured, driving a Ford Ranger pickup truck stated that the claimant, driving his Fiat 500, squarely rear-ended her vehicle. The claimant insisted that he was in the leftmost lane of two lanes, and the insured vehicle was in the right lane overtaking him. He said the Ford changed lanes to the left across the right front of the Fiat. The left edge of the rear bumper of the Ford hooked on the edge of the Fiat bumper cover and pulled it off the Fiat. The loose bumper cover then pivoted down and scrapped on the pavement until the claimant was able to pull over.

The Ford was a pickup weighing approximately 3,485 pounds. Twelve photographs were presented for our review. The images showed a relatively well-maintained vehicle with no obvious body damage other than to the back left corner area. There was obvious direct contact to the back left body panel where the left bumper corner sat. The vertical height reference showed the rear bumper to sit approximately seventeen to twenty-three inches from the ground. There was an indentation to the sheet metal above the left bumper corner, and the back left tail lamp was taped into place.

The rear bumper was metal. The left bumper corner itself did not show any discernable direct contact, deformation, or damage.

There was no evident direct contact to the rear bumper face, across the width of the back of the vehicle. The far right corner of the bumper appeared to be tilted slightly downward, in relation to the positioning of the left corner. Notably, there was no longitudinal crush to the bumper or evidence of longitudinal compression from the rear, as one might expect from a “square” rear impact from the Fiat.

The Fiat weighed approximately 2,363 pounds, and forty-two photographs were presented for review.




There were photographs of the front with and without the bumper cover in place. The images showed obvious direct contact damage to the front bumper cover. The front plane of the cover had an area of direct contact scratching, right of the center-point. The lowest portion of the cover, being that nearest to the ground, had a black plastic molding piece that was heavily scraped across its width, though predominantly on its left half. The right side of the cover that wrapped around to the right wheel well had direct contact in the form of scratching and fracturing of the plastic.



The portion of the cover wraparound that formed the front of the wheel well was broken. The wraparound on the left side was also slightly cracked. Images of the front with the bumper cover removed show there was no longitudinal crush or deformation to the bumper reinforcement bar or other underlying components. Note that only the bumper cover became dislodged, and not the bumper assembly. Images of the underside of the cover and attachment points showed damage to the brackets that held the cover in place. Notably, the cover did not show any evidence of an impact to the front plane. The overall appearance of the damage suggested an impact where the right side of the bumper cover specifically, the right front wheel well, was struck, and the force pulled the cover forward from its mounting points.

When considering the two versions presented, the Ford did not display direct contact damage to the back plane. There was no longitudinal compression to the bumper, anchors, or body panels. The damage presented was at the far left corner and appeared to be caused by an oblique force, not directly from the rear.

In conclusion, the collision version given by the claimant was the most probable one, and was supported by the photos of the damage to the two vehicles. The red Fiat was the victim, not the cause of the collision.

A freeway chain reaction

The case of the month involves a four-vehicle series of impacts that occurred on a freeway before sunrise. The first vehicle, a Ford F150, stalled. It displayed no vehicle or hazard warning lights. The second driver in a Camry failed to see the Ford quickly enough and rear-ended it in the darkness. Our client’s son was driving his dad’s Mercedes-Benz, and he, too, failed to slow for the stopped vehicles, neither of which displayed any lighting. At the last moment when he did see them, he swerved to the left in an effort to avoid them and, in so doing, crossed into the path of an overtaking fourth vehicle, a Chevrolet Tahoe. The Chevrolet then struck the Mercedes-Benz.

The California Highway Patrol investigated the incident and found both the second and third drivers at fault, as per CVC §22350: unsafe speed for conditions. The Mercedes-Benz was also found to have made an unsafe turn on a freeway, per CVC §22107.

GEI was assigned to make an independent examination of the supplied documents and photographs, to determine the impact speed and g-forces, and likelihood for injury in this incident. We were also asked to determine the sequence of events and to evaluate if the Mercedes-Benz’s driver’s statement, given in a summary of facts in the police report, was consistent with the evidence.

Our expert examined the supplied vehicle photographs, repair estimates, and the police report for this incident. He researched the weights and measurements for the Chevrolet and the Mercedes-Benz. He evaluated the National Highway Traffic Safety Administration stiffness data that relates to the vehicles’ resistance to impact damage and equated it in terms of kinetic energy. He researched the position of the moon, its luminance, and the sun’s position and lighting for the date, location, and time of the occurrence.

The photographs and repair estimate for the Mercedes-Benz showed the right rear-end to be more impacted than the center or left side of the rear-end. The Mercedes-Benz weighed about 3,293 pounds. The Mercedes-Benz has a bumper system rated to accept a strike of 5 mph, and the Chevrolet has no requirement to be rated. The Chevrolet weighed about 4,828 pounds. The Chevrolet was struck on the right front fender. The repair required three hours of frame rack time. There was bumper, grille, right suspension, air cleaner, headlamp, fender, and wheel damage to the vehicle.

The expert compared damage to landmarks contained in the weight/measurement data, and estimated the crush damage to both vehicles. He used this information and NHTSA stiffness data to estimate crush energy to the vehicles. He then totaled the damage energy and attributed it to the Chevrolet’s impact speed-differential.

He determined that the Chevrolet was going at least 13 to 22 mph faster than the Mercedes-Benz, at impact. He used this range of 13 to 22 mph in order to construct a worst-case scenario. Using 13 to 22 mph as an impact speed, and accounting for the coefficient of restitution and the great weight difference in the vehicles, the speed change (Delta V) for the Mercedes-Benz was about 9 to 16 mph. This meant the Mercedes-Benz was accelerated by the impact to a speed 9 to 16 mph greater than before the collision.

The speed change for the Chevrolet was found to be in the range of 6.3 to 11 mph. The Chevrolet was slowed when it hit the Mercedes-Benz.

In order to calculate the applied force, one must determine the time over which the majority of the force is transmitted. This is known as the impulse time. Generally speaking, data shows that impulse time is .085 to .100 seconds (100 milliseconds). When this value was factored into the mix, it was calculated that the applied force to the Mercedes-Benz was about 4.9 g to about 7.5 g.

Vehicle g-forces are not a direct measurement of forces to the occupant. Of more importance is the force transmitted to the affected areas of an occupant’s body. Seat back restitution, interior padding, seat belts, air bag restraints, and headrest positioning are all factors that can influence occupant g-forces. The force, as calculated for the acceleration to the head of the occupant of the Mercedes-Benz, was about 12 g.

How do these data compare with published threshold injury data? Research has determined that in a retroflex impact, an occupant needs a speed change of over 7 mph coupled with a force of 14 g to produce complaints of pain to healthy test subjects.

In order for an occupant to suffer an injury, the occupant must either undergo a speed change or a direction change within a very short period of time. This incident provided no mechanism for the required speed/force changes. This was not an injury-producing event, as the forces and speeds exchanged between the Chevrolet and the Mercedes-Benz were less than those reported in the literature.

The driver of the Mercedes-Benz stated that it was dark, and there was no moon. Astrological data showed that there was 81 percent illumination of the moon. It was below the horizon and was in the western sky. The accident occurred at 5:45 a.m. and civil twilight began one minute later at 5:46 a.m. Sunrise was at 6:11 a.m., twenty-six minutes later. This indicates it was not dark, but the ambient lighting was crepuscular in nature.

Per his statement, the driver of the Mercedes-Benz was watching people on the side of the road. Even if both vehicles of the preceding collision had no illuminated rear lights, California Vehicle Code §24607(a) requires all vehicles to be equipped with red reflectors visible from 350 to 100 feet from the rear when directly in front of lawful upper headlamp beams. Had the driver of the Mercedes-Benz been observant and driving at a safe speed, he could have seen the required red reflectors on the stopped vehicles in his path.

While the Mercedes-Benz driver was charged with the Primary Collision Factor, there were Associated Collision Factors that may be considered as well.

California Vehicle Code §24250 requires the vehicles stopped in front of the Mercedes-Benz to have lights in operation after the hour of darkness. CVC §24252 requires a driver to maintain his lights. CVC § 24002 requires the driver to not drive an unsafe vehicle, and CVC § 24252(a) requires a stopped driver to have a battery system capable of operating the vehicle’s lights for a period of at least fifteen minutes, if the vehicle becomes disabled.

In conclusion, the Mercedes-Benz driver could have avoided the accident, had he been alert and traveling at a safe speed, yet the drivers of the Ford and the Camry shared some responsibility for the accident by not keeping their lights on, post-collision. The good news was that there was no mechanism for injury at the speeds of this crash.

A desk top review

Our case of the month is a Desk Top Review, or DTR.   The DTR is a review of photographs, statements, police reports, and repair documents, without a physical inspection of the evidence. The DTR provides an economical and impartial review of the case when damages are minor and the vehicles have been repaired or are otherwise unavailable for physical inspection.

This particular incident involved two vehicles, both with damage to their left sides. The insured (who was not available for a statement due to other legal issues), told his wife (who reported the story to the adjuster), that he was traveling east when the other vehicle, a small import, was speeding and sideswiped his van.   In another version to his wife, he said that the other car backed into him (but that was apparently superceded by the sideswipe story).

The other driver said that he was westbound when the insured turned sharply to the left in front of him and sideswiped his vehicle.   GEI was assigned to make an independent examination of the documents and photographs, to determine the correct version of the two conflicting statements, and to determine if the vehicle-to-vehicle damage profiles matched each other.

First, the photographs of the insured vehicle, the van, were reviewed.   These  showed a slight horizontal scrape down the left side of the vehicle at a height of 19 to 23 inches above ground level.

Then, photographs of  the claimant import vehicle were reviewed.   The import was damaged on the entire left side.   Our expert compared the measurements and landmarks contained in the supplied photographs to a weights and measurements database published for the accident reconstruction industry.   The  profile showed the damage was applied in a front-to-back motion, and was 17 to 37 inches above ground level.   He found that the damage on the left rear quarter panel was about 17 inches on the lower aspect of the profile, and was 33 inches on the top of the damage profile.

The left front corner of the import, at the headlamp assembly, was also damaged.   The center of the headlamp assembly was listed as being 26 inches above the ground. The van’s damage height was 19 to 23, the import’s headlamp height was 26 inches. The damage heights of the two vehicles just did not match one another.

Next was the mirror damage.

The adjuster’s close up photographs showed minor friction marks on the import’s left rearview mirror (such as would happen if the vehicle gently brushed a wall) but it was otherwise undamaged.

This mirror was just above the level of the bottom of the windshield, which was listed as being 37 inches above ground level.  This also did not match the van’s 19 to 23 inch high damage.

The damages to the import, while not deeply intrusive, were severe enough that clearly deposited vehicle-to-vehicle paint transfers should be present, particularly since the two vehicles were painted very different colors.  There were no paint transfers in the photographs.   The damage to the import’s left rear quarter panel, at the tail lamp, was fairly deep and showed movement from front-to-back.

The damage profiles did not support either of the scenarios offered by the participants. The damage on the import was not proximate to the van and the damage to the van was not proximate to the import.

This analysis was not an accident reconstruction, the expert’s opinion was based on the documents and photographs supplied by the client.   His conclusion was that neither the insured’s nor the claimant’s statements matched the evidence that was presented.

Two DTRs-parallel parking and a rear ender

# 1: The parallel parking DTR

The insured backed his small SUV into the side of the claimant’s sedan during parallel parking.  The claimant and his passenger both claimed injury.

GEI was assigned to examine the supplied documents and photographs to determine the impact speed, g-forces, and likelihood of injury.

The photographs and estimate for the insured’s SUV showed no damage. The claimant’s sedan was slightly damaged.  His photographs showed an 8 to 10 inches wide, 1/2-inch deep dent in the left door skin.

The weight and stiffness values for vehicles were researched and speeds were calculated.   Since there was no damage to the insured’s SUV, all of the energy used in the impact was used in deforming the claimant’s sedan.

The speed of the insured’s SUV, at impact to the claimant’s sedan was calculated as 1.4 mph.  This is less than the values given for 15th percentile pedestrian-street-crossing, walking speeds.  This value was not high enough to move the claimant’s sedan sideways, a requirement for the production of an injury.  The actual movement of the claimant’s sedan immediately post impact was only to slightly rock on its springs.

How did these values apply to the production of an injury?

Vehicle g-forces are not a direct measurement of forces to the occupant.  The force transmitted to the affected areas of an occupant’s body are more important.  Seat back restitution, interior padding, seat belts, air bag restraints, and headrest positioning are all factors that influence occupant g-forces.  In this case, the forces as experienced by the claimant’s vehicle were so low that the occupant g-forces in this event were far less than those required for injury.

How do these data compare with published threshold injury data?  Research has determined that in a retroflex impact, a normal occupant needs a speed change of over 7 mph coupled with a force of over 14 g to produce complaints of pain to healthy test subjects.  Lateral load requirements are a little lower.

To give the reader a feel for what forces are involved, we can compare this event with those forces experienced by riders in amusement park bumper cars.  Speed changes (omni-directional) of about 4.7 mph, and g-forces of about 2.13 g are normal and routinely experienced.
Federal New Car Assessment Program (NCAP) data tells us the act of simply stepping off a curb produces g-forces of about 5 g.  Other examples of g-loading are as follows: sneeze, 2.9 g; being jostled in a crowd, 3.6 g; hopping off a step, 8.1 g. This incident was well under these values.

In order for an occupant to suffer an injury, the occupant must either undergo a speed change or a direction change within a very short period of time.  This particular incident provided no mechanism for these changes.  This was not an injury-producing event, as the forces and speeds exchanged between the vehicles were just too low.

# 2: The rear ended DTR

The insured (V1) was rear-ended (by V2).  Neither supplemental restraint system deployed.  The CHP responded, interviewed the participants, listed no independent witnesses, recorded no roadway evidence, and classified the damage to both vehicles as “minor”.  Their report located the damage on the insured’s vehicle as being in the center-rear.  When the claim got to the desk of the adjuster, the insured’s vehicle was heavily damaged on the right rear corner.

GEI was assigned to make an independent examination of the supplied documents and photographs to determine the impact speed, and to answer the question, “Could the vehicles have collided as described?”

We examined the photographs and the repair estimates for both vehicles, researched the published weight and measurement data, and the NHTSA stiffness values.

NHTSA stiffness values are data based upon controlled test crashes designed to produce data relative to speed from damage assessments.

The photographs for V2 showed the front bumper assembly to have been undamaged.  The center portion of the leading edge of the hood/grille assembly was pushed to the rear 2 inches.  The structural portions of the front-end were not engaged, as the force of the impact went over the bumper and into the soft, unsupported hood and grille over a width of about 40 inches.  The radiator core support was damaged. The top of the front bumper was listed as being 20 inches high.  V2 required zero hours of frame work repairs.  The 2.5 mph rated bumper’s energy absorption system was not touched.

V1 was damaged to a much greater degree. Photographs and repair estimates showed that there was damage to the rear bumper cover, to the energy absorption system, and 8 hours of work on the frame.  The floor pan and other rear quarter parts were damaged.  The right rear tail lamp was damaged, requiring replacement, and the right rear sheet metal was pushed to the front about 6 inches.    The damage seen on the right rear tail lamp was grossly disproportionate to the damage found on V2’s matching counter-point, the hood/grille.

After assessing the damage to V1, we calculated the kinetic energy needed to produce the damage to the vehicle.  This value came out to be 9,975 pounds per feet of energy.  The energy estimated from the crush values for the damage to the front end of V2 was calculated to be 1,722 pounds per feet.   Since Newton’s Third Law of Uniform Motion states that for every force there must be an equal and opposite force, the same force seen on V1 must be present on V2.   In this case, they were not.   Even when one accounts for errors in estimating damage levels, the levels could not be reconciled.  The difference was about 579 percent.

These two calculations showed the values to be so grossly divergent that they were far beyond any reasonable percentage of error. This event claimed (that required 8 hours of frame work to repair) was clearly not caused by V2.  The CHP officer saw one event, but another later event was turned in to the insurance company for payment of repairs.  Any claim of damage or injury to V1, or its occupants from V2, was just that –  a claim that was in no way supported by evidence or physics.