An alternative curve in the use of high speed transportation systems

Abstract

Consideration of extremely high speeds on railways and motorways have improved the importance of the relationship between the horizontal and vertical geometry of roads with respect to road dynamics. Many investigations have been carried out on developing new curves, which can be used for the design of horizontal geometry of roads and have many advantages with respect to road dynamics. The ideal case for compound curves formed by more than one curve, is to have no breaking point on the diagrams of curvature and superelevation, and to have a continuous function of lateral change of acceleration. As the speed increases, discontinuities on the function of lateral change of acceleration decrease traveling comfort, and increase maintenance and repair costs. In this research, a new curve joining a straight line with a circular arc provides the condition of second degree contact to joining elements related with properties of road dynamics, are examined. The layout parameters of the curve are given and the functions of curvature, superelevation and the lateral change of acceleration are examined. The new curve is compared with the classical transition curve in five different motion models.