G.M. Mackay

Chest and abdominal injuries caused by seat belt loading

Injuries will inevitably occur when restraining loads are exerted on a car occupant by a seat belt during a crash. This study investigated the nature, frequency, and severity of such injuries to the chest and abdomen. Vehicle, occupant, and injury details were obtained from accidents occurring in the Midlands of England. The sample was chosen with emphasis on fatal and serious injuries while also representing slight injuries as rated by the British government scheme. All causes of injuries to 3,276 front-seat restrained occupants were considered. 29.6% had a minor (Abbreviated Injury Scale [AIS] 1) injury caused by seat belt loading, more than from any other cause. The study went on to focus on 1,025 occupants sustaining injuries caused solely by seat belt loading. Of those, 19.4% sustained chest/abdominal injuries rated at Maximum AIS > or = 2 with sternum fractures predominating, and 4.5% were rated at Maximum AIS > or = 3. Occupants were not excluded if they had injuries at other body regions enabling the frequency and severity of head injuries to be considered also. The role played by impact type, speed change at impact, seat belt usage problems, and some aspects of occupant characteristics were investigated. While females were at much greater risk of serious injury (AIS > or = 3) when aged > or = 70 years, the effects of aging were more obvious in the cases with chest injuries rated at AIS 2. Serious chest injuries were predominantly a function of higher speed changes at impact. Occupant height and weight were shown to influence injury outcome, and the study concluded that work is required to further define occupants most at risk. Comparisons were made with two studies into other types of injury at other body regions, and injuries rated AIS > or = 2 caused by seat belt loading were seen to be relatively unlikely. It must also be stressed that casualties sustained seat belt injuries would most likely have received more severe injuries had a seat belt not been worn.

Vertebral column injuries and lap-shoulder belts

OBJECTIVE To present cases of vertebral column fractures or fracture dislocations that occur to restrained front seat occupants where there is no evidence of body contact with interior car components based on both medical records and car inspection. MATERIALS AND METHODS Reviewed were car crash injury cases investigated at the University of Michigan Transportation Research Institute and at the University of Birmingham (England) as well as the National Accident Severity Study files of the National Highway Traffic Safety Administration. Medical records and car inspections in the cases presented did not indicate any evidence of body contact with interior car structures. MAIN RESULTS Vertebral fractures or fracture dislocations sustained by front seat occupants who were wearing lap-shoulder belts are rare, as evidenced by the relatively few cases identified in the literature and in the crash injury files reviewed. CONCLUSIONS Infrequently, in frontal crashes, vertebral fractures or fracture dislocations can occur to lap-shoulder belted front seat car occupants without head or torso impacts with interior car structures. Cervical spine injuries are due to neck flexion over the shoulder portion of the restraint. Thoracolumbar fractures can occur in the frontal crash even at low crash velocity.

HOW DRIVERS SIT IN CARS

This paper presents results from a study to measure the separation of the drivers head and shoulder to various internal features of the car. Drivers were filmed whilst driving in general traffic flow, hence were unaware that they were involved in a study. The results show that certain sub-groups of the driver population are likely to be more at risk for certain impact types. Small females are considerably closer to the steering wheel than the rest of the population, and therefore prone to head strikes in frontal impacts. Large males are likely to interact with the cant rail and B-pillar in side impacts.

Restrained occupants on the nonstruck side in lateral collisions

Of injury-producing collisions with high seat belt use, some 25% to 30% are lateral collisions. This paper describes some of the characteristics of those collisions as they relate to the front-seat occupant sitting on the side opposite to the impact. The data came from a stratified sample of in-depth crash investigations conducted in the Birmingham region in the period 1983 to 1989 involving current model cars. Crash severity was assessed using the Vehicle Deformation Index (VDI) of the Collision Deformation Classification (CDC) ratings and velocity change. Injury severity was assessed using AIS 85 for each body region. 193 cases of restrained occupants in nonstruck side collisions were examined. Of those occupants with head injuries of AIS < or = 2, 35% came out of the shoulder section of the seat belt. Of abdominal injuries of AIS < or = 2, 72% came from the seat belt itself. Interaction between front seat occupants was not a frequent cause of injury to the nonstruck side occupant. Some aspects of seat belt geometry might be changed so that the trajectory and loading of the nonstruck side occupant are improved.

Restrained front seat car occupant fatalities - the nature and circumstances of their injuries

The circumstances of a rural and urban sample of fatalities in vehicles less than six years old is described. The data originate from an in-depth, multidisciplinary study of accidents conducted in England since 1983. The sample is biased towards collisions that result in occupant injury, and this paper will concentrate on those accidents in which an occupant has been fatally injured. The initial police reporting of the fatalities included 11% of the deaths occurring from natural causes. Of the crash-related deaths with complete data, some 43% were frontal and lateral impacts, and they are analysed in greater detail. Thirty-six percent of restrained occupants died in lateral collisions. In both frontal and lateral crashes, large amounts of intrusion result in direct loading of the head and chest, particularly. Under-run crashes with large trucks constitute 30% of frontal death cases, and only 12% of fatalities received fatal injuries from belt loads. Of those cases, additional loading by unrestrained rear passengers could have been an important feature. Multiplicity of severe injuries is the rule for restrained fatalities, with head injuries as the most common cause of death. Eighty-two percent died within an hour of their crashes. Some consequences for vehicle compatibility in crashes are discussed.

Maxillofacial injuries following steering wheel contact by drivers using seat belts

Maxillofacial injuries are common sequelae in road traffic accidents. For the restrained driver, impact against the steering wheel is the most prevalent cause of injury. A sample of drivers restrained by seat belts with facial injury caused by the steering wheel was taken from data at the Accident Research Unit, University of Birmingham, UK. Two hundred and forty facial injuries occurred in 135 drivers, and these are described. Superficial contusion, laceration and nasal fractures predominated. There were 504 injuries at other body regions, and these were often caused by other vehicle components. These were, for 57% of drivers, no more serious than the facial injury caused by steering wheel contact. The role of steering wheel design in maxillofacial trauma is discussed and new solutions briefly reviewed.

LEG INJURY RISK IN FRONTAL COLLISIONS

This paper describes lower limb injuries which might be assessed for current or proposed barrier tests for belted drivers in frontal impacts. Injury and impairment were rated using the Abbreviated Injury Scale (AIS) and the Injury Impairment Scale (IIS). Both emphasised the importance of fracture, especially to the ankle/foot region. AIS equal to or greater than 2 and IIS equal to or greater than 1 injury rates were high with small driver side (right side) overlaps. However, a high rate was also found for wide overlap impacts with driver side load concentration. Passenger shell intrusion was frequently associated with injuries of AIS equal to or greater than 2 and ISS equal to or greater than 1. Injuries of this type occasionally occurred with low intrusion and at low impact speeds. The injuries will be important in view of the frequency of those types of crashes in the tow-away population. Femur and ankle/foot fractures were sustained predominantly by the right limb. It is recommended that further experimental work is carried out. The aim is to determine the specific injury mechanisms involved with different intrusion levels at given impact speeds. (A) For the covering abstract of the conference see IRRD 875833.

SEAT BELT LIMITATIONS IN COLLISIONS THAT INVOLVE NO COMPROMISE OF THE PASSENGER COMPARTMENT

This is a field study of cars that sustained very little passenger compartment intrusion in frontal crashes. It has been possible to define the key limits on seat belt effectiveness in these, the most common type of crash. Data are taken from the in-depth investigations by the Co-operative Crash Injury Study and Rover Group in the UK. Vehicle crashworthiness is assessed in detail and then matched with medical information from coroners reports, hospital records or questionnaires sent to survivors. The study describes and compares important injury mechanisms such as driver head to steering wheel contacts, front passenger torso injuries caused by seat belt loads and front occupant leg injuries. 14% of occupants were rated two or above on the Maximum Abbreviated Injury Scale. It is realistic to design seat belt systems for use in passenger compartments that can be expected not to deform in the more common frontal crashes. The discussion is concerned with the importance of these results when developing safety systems in that context. (A) For the covering abstract see IRRD 893297.