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July 2012 www.sname.org/sname/mt remaining alternatives with the goal of rec -ommending a single concept with which to continue. Like the stage 1 model, the stage 2 model accounted for the track infrastruc -ture in the East Basin and the lifting capacity of the marine terminals. e major change to the stage 2 model was the ability to con -strain the number of arrival and departure tracks and storage tracks. Thus, if a train arrived at the port and needed an arrival track, it would have to be held out until one was available; the same train also required available storage tracks to hold the cars after arrival. For imports, loaded cars could not leave the marine terminal to be stored in PBY until a track was available there; keep -ing them in the marine terminal could prevent the terminal from continuing to lift. A second change reflected another potential strategy for adapting to a smaller PBY. Because some of the marine termi -nals have relatively long tracks on their property, the model was changed to enable westbound trains to arrive directly to the terminals when space was available. Note that this depends on overall volume increas -ing enough so that the railroads are willing to send a train with all cars destined for a single terminal. (is is not currently the case; almost all trains arrive at the ports ?mixed,? with cars and containers for sev -eral of the marine terminals, or even for both the POLA and POLB port complexes.) Because there were two remaining design families, each with several size variations, the model was built so that the number of storage tracks and the number of arrival/departure tracks are inputs: the number of tracks could be changed from run to run. (is also enables the analysis of build schedules.) Unlike the stage 1 model, where the result could be read from a single graph of pier B tracks in use, the analysis of the stage 2 model required iteration. For each of the concepts, the model was run with the (initially assumed) full 35% of volume that would handled by on- dock intermodal. During the simulation, th e model tracked the number of contain -ers in each of the marine terminals. The number of import containers in a termi -nal would increase when a vessel arrived, and decrease as containers were lifted onto rail cars and brought to PBY for assembly into eastbound trains. Ideally, the number of import containers reached zero slightly before the arrival of the next vessel. If PBY was unable to fully support the activity, then the number of containers at one or more of the terminals would not reach zero, but instead would increase week over week. When this occurred, the on-dock intermo -dal volume for that terminal was adjusted downwards from the original 35% and the model was re-run. is was repeated until PBY could support the volume (see Figure 3). Stage 2 model conclusions The stage 2 results suggested that after 2020, the smaller 10th Street alternative will probably be unable to maximize on- dock rail at all of the terminals. The 12th Street alternative appears to provide su -cient rail support, such that the capabilities of the terminals themselves became the limit of on-dock rail capacity. is informa -tion, along with cost estimates, economic and cost-benet analyses, environmental Pier A at the Port of Long Beach. e stage 2 model accounted for the track infrastructure in the East Basin and the lifting capacity of the marine terminals.