Exact and Heuristic Optimization Algorithms for Auto-Rack Loading Problem

Abstract

The transportation of new vehicles over the rail network takes place in specially designed railcars / wagons called auto-racks. This paper introduces a new problem – Auto-Rack Loading Problem (ARLP), involving transportation of vehicles on auto-racks with the objective of maximizing the revenue from the loaded vehicles subject to constraints. Existing literature only addresses methods to model and optimize transportation of vehicles on trucks called the auto-carrier loading problem. Initially, a model is formulated as an integer programming problem which is proven to be NP-hard since a special case of the ARLP reduces to a 0-1 multiple knapsack problem. Consequently, a multi-phase heuristic procedure is developed to solve large instances of the problem in reasonable time. The performance of the integer programming model and the heuristic procedure are evaluated and compared with an upper bound for randomly generated instances involving auto-racks and vehicles designed for use in the Indian rail network.