Six dump trucks are used to haul coal from the entrance of a small mine to the railroad. Figure provides a schematic of the dump truck operation.

Each truck is loaded by one of two loaders. After loading, a truck immediately moves to the scale, to be weighed as soon as possible. Both the loaders and the scale have a first-come first-served waiting line (or queue) for trucks.

Travel time from a loader to the scale is considered negligible. After being weighed, a truck begins a travel time (during which time the truck unloads) and then afterward returns to the loader queue.

The distributions of loading time, weighing time, and travel time are given in Tables together with the random digit assignment for generating these variables using random digits.

The purpose of the simulation is to estimate the loader and scale utilizations (percentage of time busy). The model has the following components: