Based upon nine years of experience in conducting in-depth, clinical motor vehicle accident investigations, the conditions and practices that have been found to be essential to the collection of reliable and adequate information are defined. The role of the director and the selection of personnel for the investigation teams and their qualifications, training, and supervision are discussed. The establishment and maintenance of relationships with the civil authorities, and hospitals and para-medical personnel with which the accident investigation teams must work, are explained. Examples from actual experience are presented to demonstrate the usefulness of the authors' accident investigation information in identifying areas where vehicle design improvement is desirable and evidence that corrective action taken by the vehicle manufacturers has proved effective.
Modulation of the occupant's movement within the vehicle by the seat belt reduces the potential for striking certain structures and decreases severity of the injuries. The seat belt also functions to direct the upper torso, especially the head, to specific interior surfaces. Design modifications of these areas are needed to prevent serious facial fractures that have been seen. Lap belted drivers contact the steering wheel rim or instrument panel in front of the wheel in head-on crashes; the front passenger strikes the upper instrument panel. Improper positioning of the lap seat belts produces serious intraabdominal injury, especially in the case of the rear passengers. Seat belt fatality cases were, in general, due to collapse and compromise of the occupant space as typified by the broadside intersection collision.
Investigations of 1967 and 1968 model cars indicate that the injuries sustained by driver impacts to the steering assembly are markedly reduced because of the energy absorbing steering column. Drivers, however, are sustaining facial injuries from impact to the steering wheel rim even in low speed crashes. In more severe head-on collisions, the driver is compressing the energy absorbing column and is striking his face on the upper padded instrument panel in front of the steering wheel. Relatively severe facial fractures are sustained by impacting this portion of the panel.
Data from 101 front seat automobile occupant fatality crashes that the authors had investigated were reviewed along with 70 front seat automobile occupants who had the more severe (AIS 3, 4, or 5) level injuries who did not die. The effectiveness of the lap belt alone, lap-shoulder belt, air bag alone, air bag with lap belt, and the passive shoulder belt were made. The estimates reveal that none of the restraints would have prevented 42 to 51 of the fatalities. The air bag with lap belt, and the lap-shoulder belt system, have the highest effectiveness for reducing fatalities (AB+LB, 34%; LB+SH, 32%). The air bag with lap belt has an effectiveness of 68% in reducing the more serious injuries with the lap-shoulder belt nearly as equal (64%). NHTSA's fatality reduction estimates are excessively high and overly optomistic compared to ours, but theirs are noticeably lower for serious injury reduction than are ours. Comparisons with other restraint effectiveness studies are also made.
This paper reviews some clinical case studies taken from field investigations conducted by the authors of actual crashes involving light trucks and vans. An attempt is made to indicate where Federal Motor Vehicle Safety Standards might possibly be applicable and to compare cases where vehicle design changes apparently reduced the severity of injuries. In particular, cases are shown where occupants were restrained and where steering column energy absorbing and rearward displacement systems have been installed.
Ejection from a motor vehicle has been considered a hazardous event with the belief that occupant impacts outside of the car are the injury causing event. Analysis of NCSS data, and of Washtenaw County, Michigan crashes indicates, that more than half of the more serious injuries (≥AIS 3) occurred within the car prior to the ejection. Also in rollover crashes, side glass areas are the main portals of ejection, with the major injury being sustained within the car prior to ejection, occurring more often in far side down rollovers.
The side impact, recently and currently the subject to of much debate, controversy and proposed NHTSA rule making, is a difficult type of crash to significantly reduce serious injuries and fatalites. Results from real-world crash investigations presents a confusing picture for the near-side passenger compartment crash. A direct relationship between the amount of crush and injury severity levels (MAIS) is not apparent. Exemplar cases of tow-a-way/injury crashes are presented at all AIS injury level of drivers in crashes with direct driver door crush damage.
NASS 80-88 passenger side impacts data were analyzed. Location of primary car damage using the CDC classification, the AIS for injury severity studies, and the interior contacts of the various body areas. Drivers alone, or with passengers were studied separately in both left and right side crashes. Direct impacts to the passenger compartment only are less frequent than to other CDC side zones. Driver interior contacts vary by body region but also by side impacted in the crash. The presence of an unrestrained front passenger appears to enhance driver injury level in left side crashes but the presence of a passenger, in right side crashes appears to moderate driver injury severity.
Frontal crashes (11-1 o'clock) were reviewed from the National Accident Severity Study file (NASS) for years 1980-87. Adult drivers and front right passengers, with lower extremity injuries of the pelvis, thigh, knee, leg or ankle/foot were reviewed. Analysis of age differences, injury contacts, and effectiveness of the 3-point restraint system were studied. Unrestrained drivers have a higher frequency of knee injuries than passengers, fewer leg injuries than passengers and both have the same frequency of ankle/foot injuries. Older unbelted drivers have more injuries to the pelvis, leg, and ankle/foot region than do young drivers. Passengers have more leg injuries. The instrument panel is the major contact for most of the lower extremity injuries. Lap/shoulder belts significantly reduce lower extremity injury frequency.
The effects of child safety seats have been well documented in the medical literature. Scattered throughout the medical literature are individual case reports of cervical injury to children restrained in child restraint systems. A review of the literature is provided identifying previous documented cases. The authors also provide new case details of children with cervical spine injury without head contact. An overview of the growth of the infant and specific details in the cervical spine that may contribute to significant cervical injury without head impact is presented.
Crash injury reduction via lap-shoulder belt use has been well documented. As any interior car component, lap-shoulder belts may be related to injury in certain crashes. Relatively unknown is the fact that cervical fractures or fracture-dislocations to restrained front seat occupants where, in the crash, no head contact was evidenced by both medical records and car inspection. An extensive review of the available world's literature on car crash injuries revealed more than 100 such cases. A review of the NASS 80-88 was also conducted, revealing more examples. Cases from the author's own files are also detailed.
From the authors' files, case examples of thoracolumbar injuries sustained by lap-shoulder belted front seat occupants, in frontal crashes, are presented. Additional cases were found in a review of the clinical literature. The biomechanical literature was reviewed, identifying laboratory studies on thoracolumbar spinal injuries. Suggested mechanisms in the production of these injuries in frontal type car crashes are postulated.
The “seat belt syndrome”, first described in 1961, identified abdominal organ injuries related to the use of the lap belt. Many articles have further documented detailed descriptions of intraabdominal lap belt related trauma. Lumbar spine distractions were later added to this injury list. Lap belt injury literature not infrequently hypothecates that some, if not all, of these seat belt syndrome injuries would be prevented, eliminated, or at least significantly reduced in frequency by the use of lap-shoulder belts. This report, based on data from crash investigations, documents lap-shoulder belt intraabdominal injuries occurring by belt loading alone, without significant intrusion and without significant dynamic flexing of the torso of the restrained front seat occupant.
Basilar skull fractures have previously been described as the result of cranial vault impacts. Such fractures resulting from impacts to the chin, face and/or orbital areas (non-cranial vault areas) have not been adequately documented. These types of fractures and the motor vehicle incidents in which the injuries were sustained will be described according to the type of crash and vehicles involved. Data on the tolerance levels of the basilar region of the skull are sparce at best. Case histories of non-cranial vault impacts, presented in a variety of crash types, document that facial impacts can be the sole cause of basilar skull fractures. A historical review of the basilar skull fracture literature is presented.
This paper presents an analysis of the NASS file (1980 - 1986). Cases were selected for near side impacts for drivers, i.e. left side of car, involving unrestrained adult drivers who were alone in the car, and who were not involved in any other collisions following the primary left side impact. Data analysis indicates that 11 % of the near side drivers had crush damage to only the passenger compartment, the ‘P’ zone, that the head, chest and abdomen predominate as the body areas of concern (AIS 3+ injuries), but that these injuries are sustained more often on structures other than the side interior.
In comparison to drivers exposed to steering-wheel airbag deployments in frontal crashes, there have been fewer front-seat passengers exposed to airbag deployments for 1) many of the cars in crashes did not have dual airbags and 2) the front passenger seat is less often occupied. Of the 826 airbag crashes detailed by UMTRI crash investigators at the time of this manuscript preparation, there were 145 front-seat passengers, exposed to instrument panel mounted airbags. Most of these front-seat passengers 124 were involved in the frontal crashes. There were 92 who were 16 years of age or older, 24 were under 12 years of age and 11 young teenagers, 13-15 years of age. Of those who were 16 years or older in frontal crashes 70% had an MAIS-1 injury. None of the MAIS-2 injuries were directly related to airbag deployments. Of the AIS-3+ level injuries, about two-thirds were not airbag related.
From the crash investigation files at the University of Michigan Transportation Research Institute (UMTRI), the crashes involving deployed airbags were reviewed. The total number of deployments is 898 of which 764 are frontal crashes with the principal direction of force (PDF) at 11-1 o’clock. Of the drivers in these frontal crashes 83% were using the belt restraint. Overall, seven of ten drivers have an AIS-0 or 1 level injury as the maximum or highest injury severity level (MAIS). Of the survivors, one in six had a moderate level injury (AIS-2) as their most significant injury and one in nine had an MAIS 3 or greater injury. Fatalities are rare. There is a difference between injury severity frequencies of belted vs. non-belted drivers. Three-quarters of the belted drivers had minor injuries compared to only half of those not belted. A difference was also noted at the AIS-2 level—belted vs. unbelted 14% vs. 23%.
At the University of Michigan Transportation Research Institute (UMTRI), 763 crashes involving steering wheel airbag deployments have been investigated in detail (as of 12/1/97). A subset of only frontal crashes, in which the steering wheel airbag deployed, and stature was known, was formed (636 drivers). In these crashes there were 201 “short” stature drivers, 165 cm or less in height (32% of all drivers). The vast majority of all drivers were lap-shoulder belted. Of these drivers, 69% sustained no injuries or an AIS-1 level injury. Of the shorter drivers there were 40 MAIS-2 level injuries and 15 who survived with an MAIS injury level of 3, 4, or 5. These higher level injuries were usually found in only one body area. Details of the injury locations and contacts are presented. Data on the taller drivers (435) were similarly tabulated. Of the taller drivers (> 168 cm), 74% had a MAIS-0 or 1 level injury.
On-scene investigations of 104 fatal accidents involving 136 fatalities have shown that ejection from the vehicle was the leading cause of the fatalities. The data indicate that the majority of these victims could have survived by the use of the simple lap seat belt. The steering assembly -- the end of the steering column or steering wheel proper -- was the leading cause of the fatalities among drivers. The majority of these driver fatalities could not have been saved even with the seat belt-shoulder harness restraint. Other than death by ejection, the instrument panel was the leading cause of death of the front seat passengers, most of whom could have survived by using seat belts. Impacts to the door caused invasion of the passenger compartment, and most occupants would have died even if restraints had been used. To decrease the number of fatal injuries from automobile accidents, future designs of automobile interiors must include adequate crash attenuation features.