Effect of vehicles' suspension on highway horizontal curve design

From the perspective of vehicles with a suspension system, some conventional highway design criteria do not adhere to vehicle characteristics. In particular, the relationship between minimum radius, super-elevation, side friction, and design speed should be modified to incorporate modern vehicle design in body rolling. This study addresses the limitations of conventional design criteria for horizontal curves. A more appropriate equation is derived. From the revised equation, roughly 12-30% of the deflected fraction of the conventional minimum radius criteria was found. In order to ensure driving safety based on the values obtained from the revised equation, an evaluation of existing highway curves is proposed. This study also suggests that highway agencies should improve unsatisfactory sections and install speed calming measures at places that cannot be modified.