A PSO algorithm for designing 3D highway alignments adopting polynomial solutions

Intelligent optimization algorithms for highway alignments have produced good results so far. However, considering the numerous constraints and factors directly implied in the infrastructure design, the researchers' efforts usually focus only on simplifying the alignment choice, supporting engineers in the design phase. Implementing strategic considerations regarding comfort and safety would be also very important. In this paper, the authors propose a method for designing improved 3D highway alignments using a specific optimization algorithm, based on a Swarm Intelligence technique, adopting an innovative polynomial transition curve as the unique horizontal curvature element, called PPC (Polynomial Parametric Curve). This geometric solution assures higher levels of comforts for users than the traditional ones (clothoid—circular curve—clothoid), because the PPC shows more gradual trends of the main dynamic variables involved while driving, and defines each whole curve through a unique element, simplifying the design procedure. The authors provide technical and operational details for improving a Swarm optimization model through the adoption of the PPC and prove the efficacy of the proposed procedure through a specific significant example