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Rollover Accidents account for almost 50 percent of fatalities that occur in sport utility vehicles, pickups and minivans, such that increased attention is being paid to these types of accidents. This paper discusses the common types of situations that lead to vehicle rollover of multipurpose passenger vehicles, and the mechanisms that precipitate these situations. Techniques to reconstruct the actual rollover process are presented, and examples are provided to illustrate common rollover trajectories. Parameters that affect variations in these trajectories are discussed. For example, the spacing or distance traveled between touch downs can vary substantially. Identification of these distances is necessary to accurately estimate vehicle rollover speeds, number of rolls and severity of each roll.

Because accident reconstruction involves the simultaneous movements of vehicles and their occupants, it is often difficult to explain the sequence of events to lay audiences. Computer video animation provides a technique which allows the relative movement of vehicles to be illustrated as a function of time, and in three dimensions. As a consequence the technique has found increasing utility in the litigation arena. However, because of the flexibility that is available in creating computer animations, their admissibility in the courtroom can be brought into question. Therefore, it behooves the animator to address key admissibility issues before constructing an expensive and time consuming animation.

Rollover frequency in single vehicle crashes is much higher for pickup trucks and utility vehicles (60-80 percent) than it is for cars (30-50 percent). Vehicle parameters affecting stability (and thus rollover) were examined to determine their contribution to the difference in rollover frequency among passenger cars, pickup trucks and utility vehicles. Logistic regression techniques were used to develop parameter estimates for the risk of rollover in single vehicle fatal crashes. Fatal Accident Reporting System (FARS) data for 1981-1 987 were used together with engineering data for 11 models of pickup, 16 models of utility vehicle and 11 models of passenger car. Separate parameter estimates were derived for the three vehicle types to predict risk of rollover in rural and urban areas.

This paper describes a simple low-cost method of obtaining overhead views of accident scenes and damaged vehicles. The camera is elevated above the subject vehicle/scene using a 30-foot telescopic fiberglass pole. The camera, a light-weight 35mm, autowind, with infrared remote control, is mounted with a camera quick shoe adapter. Techniques of operation of the pole and camera are described, and optimum settings for camera angle versus field of view are provided. Because the camera operator cannot physically see what is being photographed, techniques to ensure adequate coverage of the subject are also discussed. To ensure that the error of measurements subsequently taken from photographs are minimized, parallax errors must be assessed. Sources of parallax error and ways to minimize them are discussed. The photographic boundaries using this camera technique were established by photographing a 30 × 40 foot grid at various pole heights and focal lengths of camera lens.

The risk of injury for particular car makes and models was examined in relation to their corresponding crash performance in the 35mph New Car Assessment Program's (NCAP) frontal barrier tests. Texas State accident data for the years 1980 to 1982 were used to determine the risk of driver injury in single-vehicle, fixed-object car collisions. The risk of fatal or incapacitating injury was modeled using logistic regression techniques so the effect of confounding factors such as car mass, age of driver. crash severity, and restraint use could be effectively controlled. The NCAP test results were entered in the model by using the values of Head Injury Criterion (HIC), chest deceleration (CD), and femur load as independent variables. Separate results are presented for restrained and unrestrained drivers.

The Maryland State Police, in cooperation with Saint-Gobain Vitrage and the Insurance Institute for Highway Safety, installed anti-lacerative Securiflex Inner Guard windshields in a number of their new vehicles. The exposure and visibility characteristics of these windshields have been monitored and compared to the experience of standard HPR windshields of similar vehicles in the fleet. The performance of the Securiflex windshields has shown visibility properties similar to standard windshields. More importantly, the superior safety characteristics of the Securiflex windshield prevented a Maryland State trooper from recieving lacerative injuries as the result of a collision in which his vehicle struck the rear of another vehicle.

This paper examines the effects that downsizing has had on occupant injury. Statistical models are derived which demonstrate the relative risks associated with downsized cars and restraint use. Then actual occupant injuries are analysed to show how the total pattern of occupant injuries changes with downsizing. Each additional thousand pounds of vehicle mass decreases the odds of a driver injury in a crash by 34 percent when the driver is not restrained. For restrained drivers, this decrease is 25 percent per thousand. Restraint use further decreases the odds of a driver injury by two-thirds. To gain the same reduction in injury odds afforded the belted driver of a 2500 pound passenger car, the unbelted driver requires a 4325 pound car. For unrestrained occupants, the instrument panel, steering assembly and windshield (in frontal impacts) are the most frequent sources of injury.

This paper reports recent work undertaken by the Oxford Road Accident Group to improve the utility of the CRASH 2 (Calspan Reconstruction of Accident Speeds on the Highway) program. Although CRASH 2 is being used extensively in the U.S.A. for accident reconstruction, its use in Europe is limited. The accident environment in Europe is sufficiently different from that in the United States that it has been suggested that the program could be of limited use under these conditions. Accordingly, to provide reliable figures as to the utility of the program under European conditions a representative sample of accidents has been reconstructed using CRASH 2: the sample consisted of 200 accidents investigated on-scene and 200 accidents investigated on a 48 hour follow-up basis. Results are presented which give the proportion of accidents that could be successfully CRASHed together with the reasons for not running CRASH.

To improve the utility of the SMAC program and to assess its limitations, twelve vehicle-to-vehicle collisions were staged and then reconstructed with the program. A variety of impact configurations were run including: 60° front-to-side, 90° front-to-side, 10° offset head-on and 10° offset rear-end. The reconstruction of each test is discussed and compared with the measured data, using the final rest positions, velocity changes, and damage profiles of each vehicle. Finally, the limitations of the SMAC program together with recommendations for improving the simulation model are outlined.

This paper reports the results of a study designed to investigate the relation between vehicle handling and accident frequency. Because evaluation of the driver control process can only be made on a subjective basis, emphasis is placed on evaluating the role of the vehicle rather than the man-car combination. Deficiencies in handling are likely to be associated with accidents involving loss of control, and it is shown that over 80 percent of loss of control accidents involve single vehicles only. This means that the single vehicle accident rate can be used as a measure of proneness of loss of control. Single vehicle accident rates are determined by model of car and the effect on these rates of other factors, such as variations in driver age and ratio of male to female driver population between the different models, are assessed.

The Simulation Model of Automobile Collisions (SMAC) computer program was developed by Calspan Corporation as an aid with which to accurately reconstruct road accidents. Part of the overall objective of the research has been to make the system “user oriented” so that users without an engineering background can operate it with ease. This has necessitated developing a START program which automatically runs the SMAC program from a minimum of input data and an iteration routine designed to optimize the input values of velocities to provide a “best fit” reconstruction to the available scene data. A summary of how the START program works is given; however, emphasis is placed in the paper on the development of the iterative routine. The theory behind the routine is given and a number of examples are then presented to show how it works. For each example the results of each successive iteration are given to illustrate the manner in which the program converges to an acceptable reconstruction.

This paper analyses the mechanics of overturning which occurs as the result of a vehicle colliding with a curb or similar obstacle. Because the duration of impact is short, the forces involved may be treated as impulsive forces and a graphical method may be used to determine the terminal velocities after the impact. The mathematical analysis is supported by results obtained from a film of an actual track test in which rollover was induced by sliding a car sideways into a curb. The motion of the vehicle after impact with the curb was also analysed in this film. During airborne motion, the car may be considered as a simple projectile and any aerodynamic effects neglected.

This paper reports the application of the Simulation Model of Automobile Collisions (SMAC) computer program to selected cases of actual highway accidents. Since SMAC was developed to allow accidents to be accurately reconstructed by operators without a detailed knowledge of engineering mechanics, recent developments have concentrated on providing a Start routine. This program automatically generates the inputs required for SMAC, including collision speed estimates, from a minimum amount of information available at the accident scene. A brief summary of how Start works is given, followed by a discussion of actual cases. The sensitivity of the final reconstruction to the various program inputs is discussed; this gives an indication of how the initial Start inputs may be adjusted to obtain a best fit with the minimum number of iterations of the program.