Determining vehicle dispatch frequency when shipping frequency differs among suppliers

Collecting is a way to consolidate freight that involves trucks picking up material from more than one supplier on each trip to a single destination. Earlier research resulted in a method that optimizes collecting vehicle dispatch frequency and that assumes that all suppliers are visited on each dispatch. This paper develops a method that determines the optimal dispatch frequency when large suppliers are visited more frequently than are small suppliers. This added flexibility allows the combined inventory and transportation costs of collecting to be reduced. The method is developed analytically and illustrated with an example.