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.
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.
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.
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.
Using the CDC (SAE J224), a comparison of the NASS data and the UMTRI field accident files (UM series) indicates a similar distribution of offset frontal crashes. Offset frontal damage occurs in 56-61% of crashes, often involving more than one third of the front of the car. Lap-shoulder belted drivers sustain more AIS 2 or greater injuries when there is interior intrusion and occur more often when the offset damage is in front of the driver. However, this may well be due to the severity of the crash. European studies have no uniformity as to offset frontal collision descriptors are difficult to interpret, or to compare one to another.
In a review of 540 crashes in which the steering-wheel airbag deployed, 38% of the drivers sustained some level of upper extremity injury. The majority of these were AIS-1 injuries including abrasions, contusions and small lacerations. In 18 crashes the drivers sustained AIS-2 or-3 level upper extremity injuries, including fractures of the radius and/or ulna, or of the metacarpal bones, all related to airbag deployments. It was determined that six drivers sustained the fracture(s) directly from the deploying airbag or the airbag module cover. The remaining 12 drivers had fractures from the extremity being flung into interior vehicle structures, usually the instrument panel. Most drivers were taller than 170 cm and, of the 18 drivers, 10 were males.
To determine the frequency of facial injuries from steering-wheel airbag deployments, 540 consecutive steering-wheel airbag deployments, investigated by the University of Michigan Transportation Research Institute (UMTRI) personnel, were reviewed. About 1 in 3 drivers sustain an injury to the face. Injuries to the area surrounding the eye (periorbital) or to the eyeball (ocular) rarely occur. The frequencies of facial or ocular injuries are the same for belted and unbelted drivers. Drivers of short stature had a higher frequency of facial injury. Females sustained ocular injuries more frequently than males. Untethered airbags were not overly involved in drivers with an ocular injury. No specific make or model car were overly represented in the ocular injury cases.
From field crash investigations conducted by the authors, a series of well documented crashes will be presented. In each, at least one occupant was wearing a lap-shoulder belt. Detailed injury reports will be presented along with photographs of car damage, occupant contact areas, and where possible, the estimated impact speeds.
This paper presents an analysis of front seat outboard occupants in frontal and rollover crashes. These occupants were lap belted, lap-shoulder belted or were unrestrained. In the frontal crash the lap-shoulder belt reduces the occurrence of the severe, serious, critical-to-life injuries, and fatalities in all regions of the body (head, neck, thorax, lower torso and extremities). In addition, there is a strong association between belt usage and the occupant escaping from the crash with no injury. In rollover crashes, belts reduce the frequency of the more severe injuries by preventing the occupant from being ejected. For those occupants not ejected from the car, belts effectively reduce fatalities and the more serious injuries.
This report presents nineeen cases of detailed field accident investigations of Toyota Cressida crashes wherein the automatic shoulder belt was worn. Specifics of the accidents and the injuries sustained by the passively restrained occupants are detailed.
A review of the UM series and of NCSS, NASS, CPIR and FARS Files, as well as Michigan accident data files was undertaken, as well as a review of the NTSB “Rear Seat Study”. From these files rear seat occupany is approximately 10%, with children 6 years of age or less being 1/5th of these. About 50-60% of those in the sear seat are adults. Most of the injuries are at the lower AIS levels, with adults being more seriously injured. Of the more serious or fatal injuries, the head and face predominate by far, in all types of crashes involving unrestrainded rear seat occupants. When belts are worn there are few seriously or fatally injured rear occupants and of these, the abdominal area predominates. From available data, rear lap-belted passengers have the same MAIS level (or less) when compared to their front seat lap-shoulder belted counterparts.
An analysis of 211 automobiles having the ball-type E.A. device (GM cars - 1972–1980), involved in frontal crashes was made to determine the relationship between driver injury and the steering assembly. The majority of the drivers had MAIS of 0 or 1 (66%). The head was the most frequently injured body region with the lower extremities next in frequency. Of the unrestrained drivers studied, 43% had a thoracic injury, the majority of which were minor. There is no correlation between injury severity and steering rim or spoke deformation, or the amount of E.A. column compression. Specific terminology for certain aspects of the E.A. performance are suggested.
This paper presents examples of passenger car crashes with 3-point restrained front seat occupants. Detailed case capsule descriptions that include car make and model, injury descriptions and severity, and contacts producing the injuries.