Intermodal traffic has been steadily increasing on the nation's railroads since the mid 1950's. Intermodal flatcar activity is now second only to coal in terms of total car loadings throughout the industry. The intermodal segment of the nation's transportation system is expected to play an ever increasing role in the future. Intermodal managers faced with increasing demands on their systems, have expressed a need for methods to aid in the development of new management techniques, economic costing models, and management information systems. The computer simulation intermodal model that is presented in this paper is designed to aid managers with the analysis of their current terminal systems and to plan for future growth in intermodal activity.

The intermodal terminal model employs discrete, next event, simulation techniques. The Q-GERT simulation language, developed by A. Allen B. Pritsker, provides the vehicle necessary to approximate the required activities and associated flow of transactions through the terminal system. Three specific types of containers and flatcars are provided for, in addition to provisions for over-the-road container pick up and delivery. Thus, the model is adaptable to complex terminal systems, including sea ports where highly specialized containers are commonly encountered with rail, truck and ship interfaces. It is possible to simulate terminal activities for any period of time required for a specific analysis. The model's simulation output can also be modified, with little difficulty, to provide estimates of specific variables of interest for a particular terminal. Provisions for the operating environment of a terminal are also included in the model. These include week-end work rules, switching rules, container consignee notification rules, types of handling equipment employed and the standard working hours for a terminal.

The primary applications of the model are viewed to be in the areas of planning and analysis for intermodal terminal current operations and future design concepts. The graphical network orientation of the model, however, could provide managers with a communications tool to apprise upper level decision makers of new concepts. Current problems, with recommended solutions, could also be visually illustrated.