Rolling resistance and aerodynamic drag

Energy use in the propulsion of road vehicles is needed to, among other things, overcoming two resistances – rolling resistance and aerodynamic drag. VTI measures these resistances on-site on the actual road.

Measurement of rolling resistance

Two methods are used to measure rolling resistance – with a measuring vehicle, or via coast down. An issue which often arises is the impact of the road surface on rolling resistance and thereby also traffic fuel use. This relationship is for instance of interest in relation with the optimization of road surface maintenance. Here, VTI's established expertise in road surface measurements is an important factor in ensuring that the measurements will generate results that are reliable.

Measurement of road surface

Measurement of aerodynamic drag

Information on aerodynamic drag is used, among other things, for the calculation of emissions factors to estimate road traffic exhaust emissions. An advantage of coast down studies compared to the wind tunnel testing typically used for measurement of aerodynamic drag, is that the measurement is conducted under realistic conditions. Incidentally, this keeps costs relatively low.

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