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A series of tire property tests have been performed at CALSPAN on the flat bed tire test machine. The tires used in the testing were inflated tires with the tread removed. Identical make/model/size tires in normal (tread not removed) condition were also tested. Three passenger car tires and one truck tire were tested. The purpose of this paper is to present comparative results of the testing and data analysis. The test results objectively demonstrate substantial differences in cornering properties. Grouping all tires together, the measured cornering stiffness of a modified tire was reduced on average to 36.1 percent of the normal tire measured properties (ranging from 24.1 to 49.4 percent; standard deviation was 7.7 percent). Overall the character of the modified tire cornering stiffness plots and other modified tire properties were demonstrated to be markedly changed.

The time/distance relationship for a heavy truck starting from a stopped position is often needed to accurately assess the events leading up to a collision. A series of tests were conducted to document the low speed acceleration performance of a Kenworth T2000 tractor- truck equipped with an auto-shift transmission. The tests included several load configurations and acceleration rates. The vehicle was instrumented with a DATRON speed sensor to measure time, distance and speed. This paper presents data from these tests and discusses low speed acceleration profiles of heavy trucks.

Using analysis of a mini-van test vehicle’s static load conditions as a guide, four different vehicle loading situation were constructed. The loading situations represent the corners of the vehicle’s center of gravity position envelope. For the testing described in this paper a single vehicle under conditions of varied load was subjected to a series of test maneuvers designed to elicit objective measure and comparison of vehicle steady-state and transient response. The purpose of this paper is to describe the test method and present the results of handling testing and limit stability testing of a 1991 Ford Aerostar mini-van/extended van under four different loading conditions. Differences observed in the plotted results of vehicle steady state response for different load condition are detectable, but small. The test results demonstrate differences in vehicle transient response for different loading configuration.

Catastrophic and sudden tire tread separation is an event that drivers of motor vehicles may encounter and, in some instances, is implicated as the cause of motor vehicle crashes and related injury or property damage. In an effort to understand how tire tread separation affects vehicle handling, a series of tread separation handling test programs were conducted. In each tread separation test program a sport utility vehicle was instrumented and equipped with steel belted radial tires that were modified to emulate tread separation between the inner and outer steel belts. The test vehicle was then subjected to a variety of open and closed loop handling test maneuvers. This paper presents the data and analysis from these tests. The research demonstrates through controlled experiments that a tire tread separation has an effect on the vehicle’s fundamental handling characteristics. It also demonstrates that the effect depends on the position of the compromised tire on the vehicle.

The time/distance relationship for a heavy truck starting from a stopped position is often needed to accurately assess the events leading up to a collision. A series of tests were conducted to document the low speed acceleration performance of a Freightliner FLD-120 tractor-truck. The tests including several load configurations and acceleration rates. The vehicle was instrumented with a DATRON speed sensor and the engine RPM was also documented. This paper presents data from these tests and discusses low speed acceleration profiles of heavy trucks

The time/distance relationship for heavy trucks starting from a stopped position is often needed to accurately assess the events leading up to a collision. A series of tests were conducted to document tractor/trailer low speed acceleration performance. The vehicles were instrumented with a DATRON speed sensor and engine RPM was also documented. This paper presents the data from these tests and discusses the acceleration profile of heavy trucks in general.

Scientific visualizations and computer animations are frequently presented to show the results of simulation models or the opinions of a reconstructionist. In these cases it is important to properly document the graphical images being presented. Proper documentation depends somewhat on the methodologies used to produce the images, but every scientific visualization, computer animation, and computer generated image should be documented sufficiently to allow others to duplicate the images. There are also some basic data that should accompany any computer generated images that will reveal the basis of the motion for all primary objects being depicted. This paper presents some basic definitions and outlines the data that is required to document scientific visualizations and computer animations.

A controlled experimental program was conducted to determine the response of humans and a human surrogate with experimental lap belt restraints in -Gz acceleration environments. In the program, lap belt anchorage position (belt angle) and belt tension/slack were varied. Human volunteers were subjected to a static -1.0 Gz acceleration for each restraint configuration. A 95th percentile male Hybrid Ill dummy was subjected to a nominal 4.25 m/s (9.5 mph), -5 Gz impact while restrained by each restraint configuration. For the -Gz acceleration, significant changes in occupant head excursion were observed with varied lap belt configurations. In general, less pre-crash belt slack and higher lap belt angles produced significant reductions in occupant vertical excursions. This research provides data for use in evaluating or developing occupant survivability systems for rollover crash environments.

Vehicles may be loaded with passengers and cargo in varying configurations that affect its mass properties during normal use. Mass properties include Cg location, weight, and mass moments of inertia. The objective of this paper is to develop an approach identifying possible passenger and cargo load configurations and accurately calculate and display their effect on a motor vehicle's mass properties. An approach is presented and discussed. The calculation method accounts for suspension compliance due to passenger and cargo loading. Overall, the approach provides more accurate and useful estimates of a motor vehicle's Cg location and other mass properties. The approach may be of use to vehicle designers, operators, and regulators, providing enhanced access to vehicle parameters which are relevant to motor vehicle safety.

The height of a vehicle's center-of-gravity (CG) is one factor that influences its handling characteristics. A number of height methods are used to measure CG within the automotive industry. This research determined which method has the greatest potential to produce accurate CG height measurements, given anticipated measurement tolerances. Several techniques for measuring vehicle CG height were analyzed mathematically. The contributions of various parameters to total error were determined and the total error inherent in each method was then compared.

Tire marks left by the vehicle prior to impact, rollover, or other event, are important forensic evidence reconstruction of motor vehicle accidents. Often these tire marks have some curvature that is measured and used to calculate the speed of vehicles prior to the event. This calculation is based on the coefficient of friction of the tire/road interface and the radius of curvature of the vehicle center of gravity (c.g.) path. There is controversy about the validity of this approach. To explore this theory, a test vehicle was driven through a series of maneuvers that produced yaw marks for direct comparison of actual vehicle velocity to the velocity calculated by the critical speed formula. Test results show the critical speed formula is inaccurate for most circumstances and does not correctly describe vehicle limit performance behavior.

A vehicle may be loaded in varying configurations that affect its mass properties during normal use. These properties include total mass, center-of-gravity (Cg) location, and moments of inertia. The ranges of these parameters, which are determined by the varied load configurations, define the vehicle's mass property envelopes. These envelopes are useful for evaluating the effect of any load configuration relative to vehicle performance/design specifications. Mass property envelopes provide a clear visual representation of a range of key parameters that significantly affect motor vehicle control. Examples are provided in this paper that illustrate the usefulness of the vehicle mass property envelopes.

Outriggers are devices that arrest vehicle rollover during handling test maneuvers to protect the test vehicle and/or test driver. Validity of data in these tests has been questioned because the effect outriggers have on vehicle dynamics is not well understood. This research quantifies changes in handling characteristics with outriggers attached to a test vehicle. Three outrigger systems of different masses were developed and tested through various limit and sub-limit handling maneuvers. Analysis of the data generated during testing indicates improvements necessary for future outrigger designs leading to better understanding of vehicle dynamics and potentially reduced injuries from rollovers.