A simulation analysis of the effects of transportation system parameters on inventory levels

The author describes the investigation of various aspects of operation of a combined truck/trailer-railroad transportation system. The system involves shipment of manufactured parts from Mexico through the United States and into Canada. The objectives were to investigate the effect of a number of variables in the transportation system upon inventory level at the Canadian distribution warehouse and to determine the minimum number of trailers required to operate the system without introducing delays which would cause the warehouse inventory to fall below a predetermined minimum level. The model is coded in GPSS/H. The author describes some of the design features of the model including the use of the BSTORAGE block in GPSS/H to implement the changing capacities for trailers on the railway trains used. The simulation of transportation system variables, such as border crossing delays, train delays or crashes, and national holidays in all three countries, is also described. A summary of the results of the various test runs of the model is given