The pickup and delivery traveling salesman problem with first-in-first-out loading

This paper addresses a variation of the Traveling Salesman Problem with Pickup and Delivery in which loading and unloading operations have to be executed in a first-in-first-out fashion. It provides an integer programming formulation of the problem. It also describes five operators for improving a feasible solution, and two heuristics that utilize these operators: a probabilistic tabu search algorithm, and an iterated local search algorithm. The heuristics are evaluated on data adapted from TSPLIB instances