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Occasionally, an accident reconstruction analyst is confronted with the task of reconstructing an accident with configurations that do not lend themselves to straightforward analytical methods. The analyst may often turn to accident reconstruction software such as the various versions of SMAC and some impulse-momentum approaches like PC-Crash and VCRware. Within these programs there is a user-input variable often referred to as the inter-vehicle friction coefficient. Default values are typically provided with these software packages, so the user often doesn't have to do anything but leave the default value in place. However, in some collision configurations realistic solutions may not be arrived at when the default value is used. This can lead to the modification of the inter-vehicle friction value to tune the simulation result; typically in an effort to force the final rest positions of the collision partners to match documented accident scene evidence.

Results from a series of repeated-impact crash tests of a 1990 Ford Taurus sedan into a rigid, vertically offset barrier are presented in this paper. The purpose in conducting these crash tests was to further investigate override/underride crush energy behavior. The testing set-up and conduct are described and the test results, including impact speed, rebound speed and residual crush profiles are presented. The results of these tests are discussed and compared to the existing crash test data for this vehicle model. Previously suggested override/underride crush energy methodologies are also applied to the new data.

In automobile accident reconstruction it is often necessary to quantify the energy dissipated through plastic deformation of vehicle structures. For collisions involving the front structures of accident vehicles, data from Federal Motor Vehicle Safety Standard (FMVSS) 208 and New Car Assessment Program (NCAP) frontal barrier impact tests have been used to derive stiffness coefficients for use in crush energy calculations. These coefficients are commonly applied to the residual crush profile of the front bumper in real-world traffic accidents. This has been accepted as a reasonable approach, especially if there has been significant involvement of the front bumper and its supporting structures. For impacts where the structures above the bumper level are deformed more than the bumper itself, this approach may not be so readily applied.

In this paper a detailed analysis of a staged two-vehicle impact is conducted. The staged impact consisted of two moving vehicles impacting in a left front corner-to-right front corner configuration. Both vehicles were outfitted with an array of triaxial accelerometers. An Anthropomorphic Test Device (ATD) was located in the driver position in one of the test vehicles. High-speed film cameras were installed on the vehicle, documenting the test dummy motion during the impact. The impact and subsequent vehicle motions were documented with offboard real-time video and high-speed film cameras. The accelerometer data from both vehicles are analyzed. This analysis demonstrates the effects of yaw motion on the determination of Delta-V and on occupant kinematics. The notion of a Principal Direction of Force (PDOF) in a yawing vehicle is also discussed.

In this paper the characteristics of on-road rollover accidents are discussed. Typical rollover scenarios are presented and the phases of rollover leading up to and including vehicle trip are reviewed. Test data from various vehicle handling test programs are reviewed. The data from a test program that included maneuvers through an obstacle avoidance course are reviewed in detail. This program included tests in which the vehicle successfully traversed the course as well as tests where intentional vehicle tip-ups occurred. Comparisons of the driver input data (steering wheel angle amplitude and steering wheel rate) and vehicle response data (lateral acceleration, yaw rate, body roll angle and roll rate) from this program are presented. A review of previous analytical models of the rollover trip phase is also included. The applicability of these models in estimating the energy dissipation/transfer and lateral impulse leading to vehicle tip-up in an on road rollover is discussed.

Concrete Median Barriers (CMB’s) are used extensively on the roadways of North America. They are most often used as permanent barriers on major freeways and highways and as temporary barriers in roadway construction zones. A drive along most stretches of roadway where CMB’s are in use will reveal multiple instances of automobile impact evidence. In this paper the characteristics of automobile impacts with CMB’s are analyzed. Specifically, the case of a yawing, side-slipping vehicle impact, where significant frontal engagement may occur, is considered. Typical damage patterns and residual crush profiles are reviewed as well as vehicle Delta-V, and Barrier Equivalent Velocity (BEV). Frictional energy losses, due to vehicle and CMB interaction, and their significance in the reconstruction of this type of collision are discussed. The vertical velocity component induced by the CMB in this type of impact is also examined.

For automotive crash tests resulting in significant test vehicle yaw rate, direct integration of accelerometer data does not yield the correct velocity or Delta-V components (even for accelerations sensed at the vehicle center-of-gravity). This paper discusses the effects of yaw rate on the integration of accelerometer data and develops a methodology to properly calculate the velocity and Delta-V at any location on the test vehicle. This methodology is applied to crash test data and compared to results observed from high-speed film. A discussion regarding Delta-V in a yawing vehicle, and its significance to occupant kinematics and injury potential, is also presented.