Optimizing horizontal alignment of roads in a specified corridor

TL;DR

This paper presents a bi-level optimization model for road alignment that integrates horizontal and vertical alignment with earthwork considerations, achieving significant cost savings in real-world applications.

Contribution

The study introduces a novel bi-level optimization approach combining horizontal, vertical alignments, and earthwork optimization, using derivative-free algorithms for improved road design.

Findings

Achieves 27% improvement over traditional designs

Provides optimal linear-circular horizontal and quadratic spline vertical alignments

Potentially saves millions of dollars in road construction costs

Abstract

Finding an optimal alignment connecting two end-points in a specified corridor is a complex problem that requires solving three interrelated sub-problems, namely the horizontal alignment, vertical alignment and earthwork optimization problems. In this research, we developed a novel bi-level optimization model combining those three problems. In the outer level of the model, we optimize the horizontal alignment and in the inner level of the model a vertical alignment optimization problem considering earthwork allocation is solved for a fixed horizontal alignment. Derivative-free optimization algorithms are used to solve the outer problem. The result of our model gives an optimal horizontal alignment in the form of a linear-circular curve and an optimal vertical alignment in the form of a quadratic spline. Our model is tested on real-life data. The numerical results show that our approach improves the road alignment designed by civil engineers by 27\% on average, resulting in potentially millions of dollars of savings.