Optimizing storage location assignment in an automotive Ro-Ro terminal

Automotive roll-on/roll-off (Ro-Ro) transportation is an efficient and competitive method for the large-scale transshipment of commercial cars. However, the low-efficiency operations and insufficient storage resources of automotive Ro-Ro terminals have constrained the development of Ro-Ro transportation. This paper investigates the storage location assignment problem (SLAP) for the arrival of cars at the yard, and it aims to improve the ship-loading efficiency and contribute to efficient storage at Ro-Ro terminals. Two deadlock situations resulting from blocked routes are analyzed in detail. Based on the Ro-Ro ship stowage plan, a car group concept is proposed to reflect the loading sequence of cars into a Ro-Ro ship. The dispersion degree is defined to describe the centralized layout of every car group in the yard. A linear 0-1 integer programming model is formulated to minimize the total dispersion degrees of all car groups. Furthermore, an indicator called the attraction degree is presented to quantify the preferred degree of each location for storing different groups of cars. A hierarchical two-stage exchange strategy (HTSES) is designed to obtain the car layout with the minimum total dispersion degree. To reduce the scale of the solved problem, a rolling-horizon heuristic approach based on closed-loop (positive and negative) feedback is proposed. Positive feedback based on the guidance mechanism describes the guidance provided by the existing car layout to arriving cars, while negative feedback based on the reformulation mechanism represents the influence of arriving cars on the car layout. A series of numerical experiments show that the proposed method can effectively produce a satisfactory car assignment plan for the management of automotive Ro-Ro terminals.