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Retarders of various kinds to augment the braking system for trucks and buses can lead to three economic benefits: brake wear may be reduced, so that long-term maintenance costs will be lower; speed of travel on long downgrades may be increased, leading to shorter total trip time; and the probability of a runaway accident may be reduced, with consequent savings in damage and injury. All of these potential savings depend on the typical trip profile for the vehicle in Question. In this paper the likely benefits in reduced brake maintenance, productivity, and accident reduction are computed for a variety of trucking operations, and data are furnished in enough detail to permit a particular user to estimate the value of adding retarders to his vehicles.

The force-versus-deflection properties of truck leaf springs are studied with respect to the influences of motion amplitude and frequency (0 to 15 Hz) upon hysteretic damping and effective spring rate. Presented test results indicate that the energy loss per cycle of motion of a leaf spring is independent of the frequency of cycling. Measurements showing the influence of the amplitude of stroking are analyzed for five representative examples of currently employed leaf springs. A mathematical method for representing the force-versus-deflection characteristics of leaf springs is presented in a form suitable for use in digital simulations of vehicle dynamics.

A full-scale vehicle testing program which emphasizes experimental determination of the rollover stability of double-bottom tanker configurations is discussed. The testing program is presented in the context of the total research program which included yaw plane and roll plane analytical studies. The baseline Michigan double-bottom tanker is found to have exceptionally low rollover stability in emergency evasive maneuvers. Vehicle modifications are described which improve stability by a factor of two. Test vehicle loading, anti-rollover outriggers, instrumentation, and modification hardware are discussed specifically. Results of dynamic handling tests and low-speed maneuverability tests are presented. Conclusions regarding the stability of individual vehicle configurations as well as overall fleet safety are reached.