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Problems with commercial motor vehicle components such as service brakes, steering controls, lighting devices, reflectors, tires, coupling devices, and other equipment can lead to accidents. Following a collision, accident reconstructionists may be called upon to determine whether these conditions were present before the crash and whether they were a causative factor. The paper gives an overview of current requirements of the Federal Motor Carrier Safety Regulations (FMCSR)(1) and Commercial Vehicle Safety Alliance (CVSA) that are related to daily vehicle inspections and commercial vehicle maintenance. Examples are presented to show how post-accident examinations detected vehicle deficiencies that were overlooked in the driver's vehicle inspection and/or fleet maintenance procedures. A discussion is included as to how such findings may be integrated into a reconstruction and cause analysis.

This paper will give an overview of the information available from different types of vehicle data recorders, and ways the data can be used in the analysis of vehicle collisions. Reference will be made to current research relating to Event Data Recorders (EDR's). The methods used in downloading the data will be presented. Preservation of this evidence and admittance into court will be discussed. Traditional uses of this data in the determination of collision severity, seat belt use or non-use, and supplemental restraint system functionality will be discussed. Examples will be provided of additional, less traditional, uses involving the correlation of data recorded by EDR's during collision events with the results of reconstructions based on accident scene and vehicle crush data. Topics will include Delta-V, pre-crash vehicle motions and operation, driver perception/reaction times, driver actions, and vehicle acceleration/deceleration.

While Delta-V has been one of the most used indicators of accident severity for vehicle occupants, its actual determination remains a mystery to many who refer to it and use it. Delta-V is a term of art applied to a rapid change in vehicle velocity caused by impact forces during a collision. The Delta-V is associated with the high decelerations, which cause it and are applied to the occupants through restraint systems and collisions with the interior of the vehicle. This paper will serve as a primer for those new to the subject and a review for those who are familiar with the subject. Previous works by the authors will be referenced and other pertinent literature and data sources will be discussed. The analytical methods and test data used to calculate Delta-V will be presented and the relationship between Delta-V and other measures of impact severity, such as Barrier Equivalent Velocity and Energy Equivalent Speed will be discussed. The use of air bag sensor data will be included.

Computer simulation and animation are used to build upon traditional methodologies for the evaluation of rollover accidents. The use of computer simulation allows for a more complete and detailed reconstruction than is possible with traditional methods. The use of computer animation allows a superior presentation of the reconstruction with detailed analytical results and real time visualization employing 3-D computer graphics. The accident scene and vehicle damage data are used together with results from rollover tests and computer simulation and computer graphics to reconstruct the vehicle path and vehicle dynamics in three dimensions. The significant previous papers, which provide the scientific basis for rollover accident reconstruction, are discussed with regard as to how this knowledge can be applied using HVE1 and 3-D Studio MAX2.

Under inflated or deflated tires are known to cause increased forward drag and lateral steering effects on vehicles. These effects are commonly suggested to be the cause of driver loss of control and subsequent vehicular accidents. The increased drag and steering effects of under inflated or deflated tires are frequently an issue in an accident reconstruction. This paper documents the results of a series of tests conducted to determine the magnitude and effects of under inflated or deflated tires on cars and light trucks. The test also establishes a method of testing that can be used to determine steering effects for other vehicles and speed conditions. Six vehicles ranging from a compact passenger car to a 3/4 ton pickup truck were tested. The test methodology was simple and produced repeatable test results up to the 45 mph speed defined as a limit for the tests.

Vehicle crush deformation and energy equivalence relationships are widely accepted as technical accident reconstruction tools for estimating the change in velocity (Delta-V) during an impact. Delta-V has been accepted as a basis for evaluating damage severity and potential injury severity. Emori, Campbell and McHenry's work led to CRASH derivative type programs which are based upon a relationship between crush magnitude and Delta-V. SMAC derivative type programs utilize these principles while generating a time dependent analysis (simulation) by maintaining a continuous equalization of forces between the vehicles during the impact phase. This paper reviews basic principles and the relationships between Delta-V, kinetic energy, conservation of momentum, and barrier equivalent velocity which must be adhered to while performing this type of analysis. Several examples and frequently seen misunderstandings of these relationships are discussed.

The understanding of vehicle and occupant motions is at the heart of vehicle accident reconstruction. Testing is frequently done to understand, verify and demonstrate accident motions and dynamics. Tests conducted with scale models can give very useful results at a fraction of the cost of full-scale testing. The test results can be used to predict and understand the motions and dynamics of the full-scale vehicles and occupants. The proper design, construction and testing with scale models and the interpretation of the test results is governed by the principles of similitude. This paper presents an introduction to the principles of similitude. These principles have been the basis for scale model testing of structures and machines by engineers for many years. This paper presents the principles of similitude and shows how these can be applied to a vehicle which becomes airborne. The results of these tests are compared with mathematical predictions of vehicle motions.

A combination of metal roof passenger vehicles, an open top convertible passenger vehicle and enclosed multiple purpose utility vehicles were subjected to tip-over-the-front-end type pitch-over tests. The resulting roof crush and occupant compartment intrusion are presented in empirical and pictorial format. The tip-over roof crush performance is discussed relative to other recent side-over type rollover literature and to the FMVSS 216 on Roof Crush Resistance for Passenger Cars.

Vehicle accident analysis relies heavily on mathematics and the principles of conservation of energy and momentum and Newton's laws of motion. In order to apply these principles, it is first necessary to know the approximate vehicle motions. The analytical procedure is interactive using a combination of model analysis and computer-aided engineering analysis to determine linear and angular velocities and accelerations. Scale accident scene models combined with aerial photography to enhance realism has been extensively utilized in evaluation, analysis and presentation of vehicular accident reconstructions to non-technical audiences. Slide and video accident animations have been produced directly from aerial photograph enhanced models and have been used successfully in courtroom presentations since the 1970's.