  Optimization of three-dimensional road alignments is a nonlinear non-convex
optimization problem. The development of models that fully optimize a
three-dimensional road alignment problem is challenging due to numerous factors
involved and complexities in the geometric specification of the alignment. In
this study, we developed a novel bi-objective optimization approach to solve a
three dimensional road alignment problem where the horizontal and vertical
alignments are optimized simultaneously. Two conflicting cost objective
functions, \emph{earthwork} cost and the \emph{utility} cost, are cast in a
bi-objective optimization problem. We numerically compare several
multi-objective optimization solvers, and find that it is possible to determine
the Pareto front in a reasonable time.
