This model informs analyses of the availability of transportation fuel in the event the fuel supply chain is disrupted. The portion of the fuel supply system represented by the network model (see figure) spans from oil fields to fuel distribution terminals. Different components of this system (e.g., crude oil import terminals, refineries, transmission pipelines, and tank farms) can be disrupted, and these disruptions can quickly cascade through the system. Estimating the locations, timing, and severity of these impacts depends on properly simulating the capability of the fuel system to respond dynamically to disruptions.

NISAC model representation of the national transportation fuels network.

The model network consists of the locations and capacities of tank farms, refineries, and terminals (the nodes of the network), and the pipelines that connect the nodes (the links of the network). Links in the model network represent either a single transmission pipeline, or, where multiple pipelines follow the same path, a bundle of several pipelines. (Note that model links are shown as straight lines connecting nodes, so the links only approximately overlay the actual pathways of the pipelines.)  In a similar way, a model node representing refining capacity consists of either a single refinery or a group of several refineries if they are located near each other and connected to the same pipelines. Sources of crude oil to the network are nodes that represent either collections of oil fields (called geologic basins) or water terminals for receiving imports of crude oil.

Model algorithms are used to calculate flows of crude oil and refined products on the network links. If demand for crude oil or fuels exceeds what the damaged supply system can provide, the algorithms must also allocate the limited supplies to individual refineries and distribution terminals. Each distribution terminal is associated with a service area in which tanker trucks deliver fuel supplies to retail outlets. The algorithms represent dynamic behavior by releasing crude oil or fuel from storage, using surge refining capacity, or adjusting flow rates on pipelines.