Railway network design with multiple project stages and time sequencing

This paper presents a spatial decision support system for network design problems in which different kinds of projects can be built in stages over time. It was developed by the World Bank and China's Ministry of Railways to plan investment strategies for China's overburdened railway system. We first present a mixed-integer program for the single-period network design problem with project choices such as single or multiple tracks and/or electrification with economies of scale. Then, because such projects can be built all at once or in stages, we developed a heuristic backwards time sequencing procedure with a cost adjustment factor to solve the "project staging" problem. Other innovations include a preloading routine; coordinated modeling of arcs, paths, and corridors; and a custom-built GIS.