Abstract
This paper describes the findings of a research project which was conducted to determine the maximum side friction available for a range of roadway curvatures, vehicle speeds, and vehicle types. It was found that motorists demand high levels of side friction on sharp curves. In fact, curvatures sharper than 500m provide very low margins of safety against skidding. Since improved superelevation rates are unlikely to increase the margin of safety to a sufficient level, the cost-effectiveness of curve flattening for rural highways in Alberta was estimated for a range traffic volumes, and central angles. (A)