Intermodal Usage

The Current Intermodal Usage Graph shows track usage for Tacoma Rail's 4 major intermodal customers. Data is collected every half hour.

Much like the Tacoma Rail's Track Usage study, tracking of the intermodal infrastructure of the Tideflats area is also under way. Many of the concepts in this article build upon the concepts detailed in the Track Usage article.

Intermodal railcars come in various types and sizes. One of the smaller type railcars is a 70' single well railcar which holds one 40' or 45' container. A well is a square shaped bowl in which a container is placed. Another type of rail car is stack car that holds two 40' containers in a well, when they are stacked. Where a single well is one of the smallest railcars, a 325' five-well articulated railcar is one of the largest. An articulation is when two or more railcars share a single truck or set of axles, thereby making it inseparable and handled as a single railcar.

The intermodal study deals with two areas of capacities: terminal and staging. The terminals' maximum capacities in the intermodal study are based on historical utilization calculations. Since the railcar lengths vary, not all the footage at the terminals can be utilized perfectly. For example, when there is room left on a track before a required break for a three well, but the next railcar in the train is a five well, the five well must go either after the break, or be moved to the next track. This creates two capacity maximums: one "theoretical" maximum, and one "real world" maximum. The real world maximum is used for the purposes of this study and is a percentage of the theoretical maximum. Thus the utilized space in a terminal can exceed 100%. Different terminals have different percentages based on the number of breaks required, so some terminals will exceed 100% of the real world maximum more often than others.

Based on the Port of Tacoma's 1:1 agreement with Tacoma Rail, there is one foot of staging track for every one foot of terminal track. If 1:1 at the terminals was completely utilized, Tacoma Rail would only have enough room for a couple run around tracks for intermodal staging. Tacoma Rail uses these to get from one side of the staging yards to the other. Tacoma Rail cannot do any major switching operations in this instance. However, as volumes increase, the amount of pure trains (all cars destined to one terminal) can increase. Pure trains minimize the amount of switching needed. Refer to the Track Usage page for additional clarification on railroad switching needs and requirements. The staging utilization number includes both inbound (westbound) and outbound (eastbound) traffic. This measures the entire impact each terminal has on the Tideflats staging infrastructure.