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A linear model for evaluating the influence of road roughness on total vehicular rolling resistance is presented. This model considers rolling resistance to be the result of three energy dissipation mechanisms:
(a) smooth-surface rolling losses,
(b) energy dissipation in the tire due to road roughness, and
(c) losses in the suspension system due to relative motion between sprung and unsprung mass.
The first of these mechanisms is completely dependent on the properties of the tire, specifically, hysteretic losses accrued from tire deformation during rolling. The other mechanisms are dependent on road profile, vehicle velocity, and vehicle parameters, as well as tire properties.
Calculation of losses due to rolling resistance are made by means of a quarter-car model to evaluate the relative magnitudes of the various mechanisms. The results obtained indicate that for rough road surfaces, the losses due to the roughness-related mechanisms are comparable to those arising from smooth-surface hysteretic losses.
The impact of reductions in highway roughness on rolling resistance and fuel economy are discussed briefly.
roughness, vehicular rolling resistance, road roughness, rolling loss in suspensions, additional tire rolling loss
Visiting engineer, University of Michigan Transportation Research Institute, Ann Arbor, MI