Determination of minimum curve radius depending on the limit value of jerk in the geometric designs of highway and railway

Horizontal curves used in transportation systems are the critical sections on the alignment. An important issue to be addressed in order to increase road safety and comfort during the design of horizontal curves is determination of the minimum curve radius affected by many factors. While designing of horizontal alignment, value smaller than the calculated boundary value of minimum curve radius cannot be used. Therefore, one of the most important boundary values which should be considered in terms of design is the minimum curve radius. Minimum curve radius which is used as design criterion on the horizontal alignment can be derived on the basis of sight lengths, the limit values of superelevation, the limit values of lateral acceleration and the limit values of Jerk (rate of change of acceleration). Evaluation criterion of the alignment geometry in terms of comfort is Jerk. During the curve design, to take into account of Jerk criterion in terms of road safety and comfort is extremely important. In this study, minimum curve radius used as design criterion is calculated to take into account of Jerk criterion. Minimum curve radius depend on the limit value of lateral Jerk are compared with the minimum curve radius depend on the other criteria and the optimal curve radius are proposed to provide comfortable and safe transportation in accordance with the road-vehicle dynamics.