Local container drayage problem with tractor and trailer operating in separable mode

In recent years, the Local Container Drayage Problem (LCDP) has received lots of studies in research as part of container transportation. This paper examines the LCDP under a special operation mode in which tractors and trailers can be separated, i.e., tractors can be assigned to a new task at another location while trailers are waiting for packing or unpacking. The problem is formulated as a vehicle routing and scheduling problem with temporal constraints. The resulting formulation can be used to solve small-scale problems. For large-scale problems, we develop a max–min Ant colony optimization algorithm to reduce the computation time. Numerical experiments with randomly generated instances are performed to demonstrate the performance of the algorithm.