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A mobile dynamometer for measuring the longitudinal force acting at the fifth wheel connection between a tractor and a semitrailer has been developed. The use of this dynamometer for testing retarders installed in tractors is described and example results are presented. Computational methods for predicting total retardation of various vehicles equipped with retarders are discussed.

A new over-the-road brake dynamometer has recently been developed to measure commercial vehicle brake torque at nearly constant speed. In this paper, results are presented from the initial test program of this vehicle. The program included tests to assess the influence of initial drum temperature and rubbing velocity on brake torque, as well as the occurrence and nature of brake fade and hysteresis effects. Results of these tests indicated that the rate of energy flow into the brake system had a more significant effect on brake torque than initial temperature. Greater hysteresis was found in the S-Cam brakes than in the dual-wedge brakes.

The current federal accident data collection system is inadequate. It does not produce representative data essential for answering cause-and-effect questions concerning accidents, injuries, and fatalities, and it does not produce adequate data essential for conducting cost-benefit analyses of changes in vehicle designs, highway designs, or driver licensing policies. A proposed federal data collection system (SIR) can solve those problems at a total cost of about $6 million a year. The SIR system would include 30 investigating teams precisely located throughout the U.S., and would include a Sampling program, an In-depth program, and a Rapid-response program. The sooner this system is established, the sooner government and industry will begin to obtain accurate and reliable answers to pressing questions in the field of highway safety.

Blunt abdominal trauma is a major cause of death in the United States. However, little experimental work has been done to clarify the mechanism of blunt abdominal injury and to quantify tolerance parameters for the abdominal organs. This paper describes a joint study by the Highway Safety Research Institute and the Section of General Surgery of The University of Michigan in which direct impacts were applied to livers and kidneys. The tests were performed in a high-speed testing machine at a controlled ram velocity and stroke limit. The organ was surgically mobilized in anesthesized Rhesus monkeys and then placed on a load cell while still being perfused in the living animal. Tests were performed at ram speeds of 120, 6000, and 12000 in/min (5, 250,and 500 cm/s). The resulting load-deflection data were normalized and average stress-strain curves plotted for each test. In addition, the resulting injury severity was estimated immediately after impact using an injury scale of 1 to 5.

An open-loop limit-maneuver test methodology was refined from an earlier study which hypothesized a relationship between vehicle performance and highway safety. Refinements in methodology were attained in the areas of test apparatus, test procedure, data processing, and performance interpretation. Open-loop response measurements were conducted on a representative sample of 12 contemporary passenger vehicles. Numeric characterizations of performance are presented, indicating the range and distribution of response properties exhibited by the vehicle sample.

Direct impact to the larynx is usually prevented in accidents by the protective nature of the chin. In some situations, the occupant motions leave the larynx unprotected and susceptible to impact by the steering wheel rim or instrument panel. As one of the unpaired vital organs of the body, there is no easy way to provide an alternative for its functions when the larynx is lost or damaged. Information available on the tolerance of the unembalmed human larynx to force is quite limited. This paper describes a multidisciplinary study to determine the response of unembalmed human larynges to blunt mechanical loading and to interpret the response with respect to clinical data. Fresh intact larynges were obtained at autopsy and tested at either static or dynamic loading conditions utilizing special test fixtures in materials-testing machines. Load and deformation data were obtained up to levels sufficient to produce significant fractures in both the thyroid and cricoid cartilages.

An engineering analysis of vehicle braking is presented in terms of the utilization of available road friction. Physical relations are derived which allow the determination of optimum brake force distribution on front and rear wheels as a function of axle loading. Ideal braking distribution curves are shown for a typical vehicle in the loaded and unloaded conditions. A technique is suggested for rational design of braking system parameters. It is applied to the case of a two-stage proportioning system, and is validated by experimental data from tests using a specially equipped light truck. It is concluded that a proper design analysis can establish a combination of braking system parameters which results in improved utilization of available friction. A simple, self-adjusting brake proportioning system can be a highly cost-effective safety device for truck use.

This paper reviews the state of theoretical and experimental technology relative to the dynamic performance of articulated highway vehicles. The review contains three major sections, corresponding to the traditional breakdown of vehicle performance: directional performance, braking performance, and combined directional and braking performance. An attempt is made to take a frankly evaluative point of view and to point out knowledge gaps and unanswered questions, in addition to documenting previous accomplishments and progress. The paper concludes with some recommendations for future research consistent with the findings of the review.

Driver-vehicle tests were performed in which the deceleration/pedal-force ratio (i.e., gain), pedal-displacement level, speed, surface-tire friction, and driver characteristics were systematically varied in order to determine the influence of these variables upon minimum stopping distance and other performance variables. Tests performed on a low coefficent of friction surface showed that high values of deceleration/pedal-force gain result in a greater number of wheel lockups and longer stopping distances compared to results achieved with intermediate or low deceleration/pedal-force gains. Tests performed on the two test surfaces with high and intermediate levels of friction showed that low deceleration/pedal-force gains produced longer stopping distances than were obtained with high gain, even though a high-gain brake system causes higher frequencies of wheel lockup.

An analysis is made of the influence of tire-mechanics characteristics on the behavior of an automobile undergoing maneuvers requiring the tires to produce combined longitudinal and lateral forces. The mathematical model employed to represent the vehicle incorporates wheel rotational degrees of freedom and relationships expressing the longitudinal and lateral tire shear force components as analytical functions of tire normal load, sideslip and inclination angles, and longitudinal slip. The tire shear force relationships, derived by extrapolating from existing theory for the traction mechanics of a freely rolling tire, agree qualitatively with available experimental data. Analog simulation results are examined to assess the influence on vehicle steering/braking response of variations of three parameters: lateral tire stiffness, longitudinal tire stiffness, and the coefficient of friction at the tire/road interface.