The road train optimization problem with load assignment

This paper studies the road train optimization problem with load assignments (RTOP–LA). The RTOP–LA deals with assigning customers’ demands to trailers delivered via regular trucks or road trains and determining the routing of these trucks through final customers. Road trains leave the origin terminal to reach intermediate ones, where the trailers can later be dismantled and sent to customers by regular trucks. We formulate the problem to minimize the total cost. A commercial solver is used to solve small-size instances of the problem, and we develop a multi-start iterated local search (MS-ILS) algorithm to obtain high-quality solutions. The results of our experiments show that MS-ILS provides optimal solutions for most instances. For small size instances MS-ILS outperforms the commercial solver, but its performance becomes more evident when the number of customers increases. Moreover, MS-ILS provides excellent solutions for larger instances in short computation times. Finally, a slightly adapted version of our algorithm has been proved efficient to solve the single truck and trailer routing problem. Compared to state-of-the-art algorithms on a set of 32 instances, our adapted algorithm obtained five new best known solutions.