[ewilliams]

Excellent question. Simulation and optimization are not mutually exclusive. I would begin with simulation, since it seems very likely you will have many sources of variation (e.g., truck breakdowns and maintenance, load and unload time variability, and variability in market demand for various products the trucks might move, to name just three). You likely also have multiple tempting performance metrics -- possibilities such as service quality (e.g., average and maximum wait times for pickup) to the raw-material moves, service quality to the finished-goods moves, capital investment cost of the trucks, operating cost of the trucks, and inventory levels. Simulation is more adaptable to (a) different objectives explored concurrently and to (b) incorporating the sources of variation into the analysis. An example of (a) is "Shall we minimize wait times under a cost constraint or minimize cost under a wait time constraint?" A simulation analysis can do each of these and more in rapid succession.