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Relative rollover conditions of a heavy vehicle are analyzed to establish an array of potential dynamic rollover indicators towards development of an early warning device. A relative roll instability indicator defined as Roll Safety Factor (RSF) is proposed and shown to be a highly reliable indicator regardless of vehicle configurations and operating conditions. The correlation of various potential rollover indicators with the roll safety factor are then investigated for a 5-axle tractor semi-trailer combination using a comprehensive directional dynamic analysis model to determine the reliability of the proposed indicators over a range of operating conditions. The indicators are further examined in terms of measurability, lead time, and potential for application in an early warning system. The study shows that the trailer lateral acceleration and axle roll angles are closely correlated with the RSF.

The longitudinal load transfer encountered in a partly-filled ellipsoidal tank truck, subject to a straight-line braking maneuver, is investigated as a function of the location of partition walls, deceleration and the fill level. The response characteristics of the truck equipped with a compartmented tank are evaluated in terms of dynamic load transfer, stopping distance, braking time and time lag between the front and rear axle wheel lock-up. The braking response characteristics are derived as a function of the load shift, and number and location of partition walls. Road tests were performed on an airport fuel truck, equipped with a 3 m long tank with two movable partition walls. The simulation results derived from the test vehicle model are compared to the road test data to demonstrate the validity of the analytical model. The results show good correlation with the measured data acquired under straight-line braking maneuvers performed under different fill levels and initial speeds.

The increased number of heavy trucks on today's highways, along with the extended driving hours, resulted in increased demand for improved driving conditions and prompted concern about the dynamic pavement loads. The dynamic pavement loads are one of the major causes of pavement deterioration. Passive suspensions, while being very reliable and easily implementable, fall short of satisfying the various conflicting design requirements. The overwhelming improvement of ride quality resulting from the use of active suspensions seems to have overshadowed their effect on tire generated pavement damage. An in-plane tractor-semitrailer model is used to evaluate the relative performance of fail-safe active and passive suspensions. Both full state feedback and limited state feedback are used in the design of the active suspension.