A note on the truck and trailer routing problem

This study considers a relaxation of the truck and trailer routing problem (TTRP), called the relaxed truck and trailer routing problem (RTTRP). In the TTRP, the number of available vehicles, namely trucks and trailers, is limited. Since there are no fixed costs associated with the trucks or trailers, it is reasonable to relax this fleet size constraint. Besides, most benchmark instances for the capacitated vehicle routing problem (VRP) do not have fleet size constraints. We developed a simulated annealing heuristic for solving the RTTRP and tested it on 21 TTRP benchmark problems. Computational results indicate that the solution for the RTTRP is generally better than the best solutions in the literature for the TTRP. Among the 21 benchmark TTRP instances, we found better solutions to 18 of them. The solutions for the remaining three problems are tied. The average improvement is about 1.33%. Considering the ever rising crude oil price, even small reduction in the route length is significant.