Optimisation of loop ramp design for cloverleaf interchanges

Abstract

In this paper a loop ramp for cloverleaf interchanges is geometrically designed by two methods. In the first design, the conventional spiral curves are used for the loop ramp while in the second approach, a methodology is proposed for designing the loop ramp with compound curves. These designs are then compared to each other using criteria which are weighted by the analytic hierarchy process (AHP). In addition, the ant colony optimisation in continuous domain is also utilised for finding the best solutions within all the possible designs of the loop ramp using compound curves. In order to confirm the accuracy of optimised solutions, their results are also compared to the best solutions of the AHP analysis method. Overall, the results demonstrate that the design of loop ramps for cloverleaf interchanges using the presented method generally offers outstanding savings in comparison to the traditional spiral design for loop ramps.