Search Results

This study presents an efficient method for forensic engineers to determine the maximum forward head, hip and knee velocities of automobile occupants who are restrained by seat belts during frontal impacts. The ratios of the peak head, hip and knee velocities as a function of the impact speed change were determined from a combination of previous research data. The time and location at which the peak velocities occur are also presented. In addition, the head velocity profile as a function of head displacement was quantified for the lap and torso restraint case. The compiled head, hip and knee velocities may be utilized in order to assess seat belt usage and benefit. The results of this study may be referenced to aid in modeling the motion of vehicle occupants in frontal impacts for a range of impact severities.

There are many mathematical and empirical models to facilitate technical analysis of vehicle-pedestrian collisions. The main objective of the technical analysis is to determine the vehicle impact speed. In the real world, post-impact data from vehicle/pedestrian collisions is often insufficient to use pure mathematical models. However mathematical models can be utilized successfully with the aid of some empirical data or reasonable assumptions. Conversely the empirical models overcome the difficulty of insufficient data, but must be applied within the model defined limits. This study compares the mathematical and empirical models. In addition, a slight variation of an earlier model [1] is presented to test the sensitivity of empirical models.

A comprehensive analysis method for assessing the vehicle impact speed in a vehicle/pedestrian collision was presented in an earlier publication (SAE #2000-01-0846) by the above authors [1]. This presented method provides a practical analytical approach for evaluating vehicle impact speed from the post-impact vehicle damage, pedestrian injuries and pedestrian throw distance. The applicability of this method to reconstructing real world vehicle/pedestrian collisions is examined. The results of this study indicate that the previously presented model can be used to assess a reasonable range for the vehicle impact speed in a vehicle/pedestrian collision. The regression model equations were revised to include the new data.

Lane change maneuvers are often implemented in typical driving applications and more severe swerving maneuvers are occasionally performed in order to avoid motor vehicle collisions. For accident reconstruction purposes, it is necessary to accurately model the vehicle motion and driver response during a lane change maneuver. A theoretical lane change model was developed in order to determine the expected vehicle dynamics including lateral, longitudinal and angular vehicle displacements during the lane change maneuver. This model is based on the vehicle speed, peak and average accelerations, and driver steering input. The theoretical model was then compared to a limited number of real world staged lane change maneuvers conducted with instrumented vehicles over a small range of speeds, accelerations and displacements. The lane change model was found to closely simulate the vehicle motion as recorded during the staged tests.

This paper investigates the accuracy of vehicle pre-braking speed estimates based upon tire/roadway coefficient of friction (drag factor) measurements and skid mark measurements. Data was collected to determine if there were any correlations between pre-braking speeds and pre-skidding speeds. Braking tests were performed on three vehicles using various measurement devices including an accelerometer, a fifth wheel, a radar gun, and a shot marker (bumper gun) system. The vehicle speeds, braking distances, skid mark distances, and deceleration histories were recorded. From this data, coefficients of friction for the tested road surface were evaluated. The coefficients of friction were then used in combination with the measured skid mark distances to calculate the vehicle pre-skidding speeds. The calculated pre-skidding speeds were then compared to the actual pre-braking speeds of the vehicles in order to establish the accuracy of the calculation methodology.

This study presents an efficient method for forensic engineers to determine the expected forward knee and hip displacements of automobile occupants who are restrained by seat belts during frontal impacts. The amount of knee displacement sustained by an occupant in a vehicular collision must be determined in order to assess seat belt usage and benefit. The results of this study may be referenced to model the lower body motion of vehicle occupants in frontal impacts for a range of impact severities. Previous research has empirically determined hip and limited knee displacements for subjects restrained in frontal impacts of specific severities; however, these research results have not been directly compared to produce a simple and practical model that is applicable for a range of collision severities.

This paper presents a comprehensive method for assessing the vehicle impact speed in a vehicle/pedestrian collision. Mathematical models, real world collision data and staged impact test data were referenced from several studies pertaining to pedestrian collisions. Applicable relationships comparing vehicle impact speed to pedestrian throw distance were developed from regression analyses. In addition, post-impact vehicle damage and pedestrian injuries were subjectively analyzed to assess trends in vehicle impact speed. These methods provide a practical analytical approach for evaluating vehicle impact speed from the post-impact vehicle damage, pedestrian injuries and pedestrian throw distance.

This study presents an efficient method for accident reconstructionists to determine the expected forward head displacements of automobile occupants who are restrained by lap and torso seat belts during frontal impacts. Data were referenced from various research investigations; thus, a wide range of different test conditions, configurations and subjects were considered. The impact severity of the tests ranged from 16 to 60 km/h. Results presented in this study provide a practical method to determine the expected head excursion for occupants who are restrained by lap and torso seat belts during frontal impacts.

This paper presents a practical analytical approach for evaluating sideswipe collision severity from residual vehicular deformation. A simplified mathematical procedure was developed to evaluate vehicular speed changes, effective average vehicular acceleration rates and the collision duration from measurements of vehicular damage. Several series of sideswipe collisions were staged to acquire empirical sliding contact data. The results of this testing were employed to provide a preliminary validation of the proposed analysis model. The limited validation supported the use of the proposed analysis technique to assess a vehicle's speed change resulting from a sideswipe collision.