A new transition curve with enhanced properties

Abstract

A new transition curve-3 (NTC-3), joining two straight lines by providing second-degree contact related to the properties of vehicle–road system without the necessity of a circular arc, is presented. The NTC-3 is offered by curvature and superelevation functions and is compared with the new generation transition curves-1 and -2 (NTC-1, NTC-2) and spiral curves. The properties of vehicle–road system, represented by function of lateral change of acceleration (LCA), are examined for these curves. Three criteria are taken into account to compare the curves. The NTC-3 and NTC-1 are compared in five-different motion models: model with constant velocity, model with positive acceleration, model with negative acceleration, model with negative acceleration – positive acceleration, and model with positive acceleration – negative acceleration. Examination of three criteria shows that NTC-3 is superior to the other curves on the basis of vehicle–road system.Key words: route design, transition curve, vehicle–road system, curvature, lateral change of acceleration, superelevation, motion model.