  The Electric Multiple Unit (EMU) circulation plan is the foundation of EMU
assignment and maintenance planning,and its primary task is to determine the
connections of trains in terms of train timetable and maintenance constraints.
We study the problem of optimizing EMU circulation plan, and a 0-1 integer
programming model is presented on the basis of train connection network design.
The model aims at minimizing the total connection time of trains and maximizing
the travel mileage of each EMU circulation, and it meets the maintenance
constraints from two aspects of mileage and time cycle. To solve a large-scale
problem efficiently, we present a heuristic algorithm based on particle swarm
optimization algorithm. At last, we conclude the contributions and directions
of future research.
