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OCR for page 39
Security Screening Model
Security screening requirements for passengers are subject to FAA/TSA regulations and the
level of security may be changed by FAA directive if unusual levels of threat are perceived. When
specific direction or counsel is needed, requests must be made directly to TSA.
The Security Screening model is designed to provide a view of the passenger experience in the
queue in relation to wait times and queue area. The user defines the processing rates and number
of lanes, and inputs the existing or desired screening lane dimensions and queue dimensions.
Figure 48 is a screenshot of the model. The cells are color-coded in the same manner as the other
models in the spreadsheet. The user makes the inputs into the white cells and can perform a
sensitivity analysis of the screening process by adjusting the inputs and observing the changes to
the wait times and passenger space values.
Additional information about the inputs or calculations in the user cells is provided by way of
cell comments that will pop up when the user's cursor is placed over the cell.
Estimating Demand
Processing rates for security screening checkpoints (SSCP) have been observed to vary signif-
icantly at different sized airports with rates ranging from approximately 100 passengers per hour
per lane to over 200 passengers per hour per lane. A lane is typically a walk-through metal detector
(WTMD) plus an X-ray machine for carry-on bags. Based on current TSA procedures requiring
passengers to remove computers and some other electronics from passenger bags, to remove their
shoes, etc., the bag X-ray machine usually determines the capacity of the SSCP. A combination
of two X-ray machines paired with a single WTMD for better TSA staff utilization is currently
the preferred configuration.
Passenger characteristics typically determine the SSCP throughput, with less frequent travelers
(who are unfamiliar with TSA rules and procedures) taking longer than frequent flyers. Changing
TSA rules (such as the ban on liquids and gels) can also slow down processing rates until all
passengers become familiar with new procedures. It is very important that each airport measure
its average processing rates during different seasons and times of day to determine a reasonable
range of rates to use for planning. It is also recommended that actual throughputs be observed
rather than relying on TSA hourly WTMD counts. These counts will overstate the passenger
throughput as it counts each person who passes through the WTMD, including TSA officers and
passengers who set off the alarm and are allowed to take off probable metal items and walk
through again. The TSA also collects alarm rates for each WTMD. These alarm rates tend to vary
depending upon the mix of passengers at the checkpoint.
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