Route selection can rely on a variety of criteria, with the most common being the minimization of costs and the maximization of economic efficiency. The above figure depicts three route selection scenarios where a path must be selected on a grid by linking its bottom left and top right corners.
- The first grid represents road construction costs, ranging from low to high. The selected route is an attempt to minimize such costs, so it follows a path composed of low-cost cells.
- The second grid represents the level of economic efficiency derived if a road crosses a cell, such as population density. The selected road tries to maximize efficiency by servicing as many high-efficiency cells as possible. It is worth noting that the low-cost route and the high-efficiency route follow different paths, which raises the question of which route should be selected. More than often, a compromise is sought.
- The third grid represents a compromise where the selected route tries to satisfy both criteria, so the path crosses cells concomitantly with low cost and high efficiency. The compromise is a sub-optimal solution since it is neither the most cost-effective nor the most efficient solution.