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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. 39