the ability of a wheel to damage a road structure is proportional to approximately the fourth power of the wheel load so that long road life will be promoted by minimising both static wheel loads and dynamic variations about them. this report investigates theoretically the dynamic behaviour of a simple vehicle model when it passes over various types of road surface irregularity; the effect of varying the model's parameter values on the dynamic loads applied to the road and on accelerations experienced by the vehicle body has been examined. the initial peak dynamic loads as the vehicle passes over a surface irregularity are shown to be most sensitive to changes in tyre stiffness (which is related to tyre pressure) and in sprung mass (i.e. changes in the payload); subsequent peaks are particularly sensitive to changes in suspension viscous damping. the first peak of acceleration of the vehicle body is shown to be particularly sensitive to changes in sprung mass, spring stiffness, tyre stiffness, and suspension viscous damping. a non-linear spring is shown to be able to reduce accelerations experienced by the body when the vehicle is unladen, with little change in accelerations when the vehicle is laden (a)

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