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 at minimizing 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 much 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 about which route should be selected? More than often a compromise is sought.
- The third grid represents a compromise where the route selected tries to satisfy both criteria, so the path crosses cells that have concomitantly a low cost and a high efficiency. The compromise is a sub-optimal solution since it is neither the most cost effective, not the most efficient solution.