Controls for Horizontal Curve Design

Abstract

Several concerns have been documented in the literature regarding AASHTO’s Green Book guidelines for horizontal curve design. Specifically, some researchers are concerned that the side friction factors are dated and do not reflect today’s drivers, vehicles, and pavements. Some also are concerned that the superelevation distribution method recommended in the Green Book, in combination with the use of multiple maximum superelevation rates, does not promote design consistency. Side friction factors and a distribution method that resolve these concerns have been developed.