Dr. Frances Greene, Transportation Security Administration
Bonnie Kudrick, Transportation Security Administration
Katherine Muse, Transportation Security Administration

The Transportation Security Administration (TSA) has three engineering psychologists within the Office of Security Capabilities (OSC) who address the human element for the Agency. While many activities and programs cannot be elaborated upon due to security restrictions, a few human factors activities will be reviewed. The human factors team is tasked with writing and reviewing acquisition documents, as well as participating in acquisition milestones that span the Acquisition Lifecycle Framework. The team also works to improve operational efficiency, training effectiveness and data mining efforts by examining how human factors and interactions can be optimized for various processes and procedures.

The Office has several ongoing research efforts with a number of different performers to investigate a range of human-centered issues. For example, through the Risk-Based Security Workforce Transformation Group, hypotheses were presented regarding the specialization of Officers at the checkpoint: image analysis, passenger interface, and effective interaction. Industrial/Organizational psychologists match job task analysis competencies with batteries of assessments to test for attitudes, attributes and aptitudes that would be predictive of these competencies on the job. Additional human-centered efforts will be discussed throughout this paper.

Keywords: Human Factors Engineering, Transportation Security, Risk-Based Screening


While recognition of the human as a key element in system design and development has been evident in various industries and government agencies for six decades, the existence of a workforce of human factors engineers is a relatively recent manifestation within the Transportation Security Administration (TSA). TSA has engineering psychologists within the Office of Security Capabilities (OSC) who address the human element for the Agency. While many activities and programs cannot be elaborated upon due to security, a few human factors accomplishments will be reviewed, after a comprehensive look at the elements within the airport passenger screening checkpoint.


Much like the Department of Defense (DoD) and industry, TSA sees the human as an integral part of a system. Unlike DoD, TSA’s user population includes not only our Officers at the airports, borders and ports, but also the entirety of the traveling public in all modes of transportation. The system to be described for the purposes of this paper is the passenger screening checkpoint at the airport. Specific interfaces with the Transportation Security Officers (TSOs) and the passenger are of interest and concern to the human factors team for a number of reasons. Please note that the six positions described below are not held by six different TSOs, each specializing in the position duties; they are in fact rotated and performed by every member of the checkpoint team.

The first interface with TSOs for the traveling public as they enter the checkpoint is called a Travel Document Checker (TDC) (see Figure 1). The TDC is responsible for validating all forms of identification, matching the face on the ID with the traveler, and determining that the boarding pass information is a match for the passenger on the ID, at the correct airport, and on the right day for the outbound flight. In support of TDC activities, the human factors team has been asked to evaluate new equipment for credential authorization as well as boarding pass scanners. The Officers’ cognitive workload, visual search patterns, system design and layout, and throughput pressure are just a few of the variables of interest.

Figure 2 shows the general lay-out of the checkpoint positions and equipment, after the TDC, including the X-ray machine, Walk Through Metal Detector (WTMD) and Advanced Imaging Technology (AIT).

The next encounter for the passenger is the Divestiture Officer (DO) seen in Figure 2 by the divestiture tables and bins, before the x-ray tunnel. The DO is responsible for providing instructions to passengers and assisting individuals in divesting items for x-ray screening, as well as helping prepare individuals for the screening process. Primary responsibilities entail monitoring and managing of the AIT / WTMD queue and instructing individuals on what to divest. The DO reminds passengers to use bins to divest personal belongings such as purses, carry-on bags, backpacks, laptops, Liquids, Gels and Aerosols (LGAs) in quart-sized bags, shoes, jackets, etc.

The DO manages the flow of passengers and bags into the x-ray machine, and his / her success in communicating and ensuring compliance with the standard screening lane rules results in fewer bag checks and pat downs due to items being properly divested.

The third position, the X-ray Officer, interprets the x-ray images of the passenger’s divested property, including luggage contents, bins, shoes and bowls. With the airlines charging a luggage fee for each checked bag, the items per person carried through the checkpoint has correspondingly increased. This avoidance of the checked bag fee by traveling passengers’ results in not only more items per passenger that are screened by the x-ray systems, but also items that are of increasing image complexity. The tasks of the X-ray operator involving visual search principles, signal detection theory, and object recognition are crucial to our airways security. The Xray Officer’s job is an understandably high workload and fastpaced position. The variety of designs of the operator control panel for the x-ray machines is one topic with which the human factors team has been consulted.

The X-ray Screener has a difficult task of visual search, whereby a decision must be made to search for a target among simultaneous distractors in cluttered carry-on bags, backpacks, purses and bowls of random metal and other objects. The size of the bounding box that the x-ray systems’ algorithms generate to highlight potential threats was the subject of a recent assessment at TSA. Duty cycle time of how long an xray position should be occupied by the same TSO is a current research effort under study. This effort includes investigating the ways in which that cycle time changes as a function of the new TSA Pre✓™ allowing laptops and quart bags of liquids, gels and aerosols (3-1-1 compliant LGA) to remain in the bag,
as well as the passenger leaving his / her shoes and light jackets on. All these elements, including the continuous belt movement, are all experimental variables taken into consideration when investigating the duty cycle and scheduling.

The WTMD and the AIT hardware are also depicted in Figure 2. Each piece of equipment has an Officer with responsibilities for its operation and passenger flow, including both a male and a female Screening Officer at the AIT (positions 4 and 5) to complete pat down procedures in the
case of an anomaly identified by the machine. The AIT is primarily used to screen passengers for metallic and nonmetallic threats, including weapons and explosives, which may be concealed under clothing without physical contact.

The human factors team could be asked to recommend options for number and types of alarms on the WTMD, as well as format and placement of the display on the AIT. The technology in place at many checkpoints was developed and deployed without many human / system interface considerations. The previous systems deployed in airports spawned a controversy beginning in fall 2010, when airports began using full-body scanners. The scanners quickly resulted in widely-publicized criticism for producing images many considered too “anatomically revealing.” TSA removed all those scanners and the current upgrade to these machines means less-revealing images through advanced target recognition technology and a more amorphous image of the passenger (an avatar). The avatar, with no anatomical features, is a satisfactory change to displaying areas of concern or interest on a passenger by highlighting areas for targeted pat downs or additional screening.

The final position in the checkpoint, Dynamic Officer (position 6), has primary responsibilities for standard pat downs and secondary bag checks, involving Explosives Trace Detection (ETD) of the bag and passenger.


These six Officer positions from the Travel Document Checker through the Dynamic Officer form a cohesive team of security personnel, augmented with hardware and software contained in the deployed technology at the checkpoint. Human factors engineers at TSA are concerned with common problems in the human / system interface: cognitive processing demands, fatigue, scheduling, team performance, ergonomics, and control and display design, just to name a few.

As in other Agencies and industries, TSA has recognized the criticality of determining all human factors requirements as early as possible. Human factors must have a seat at the table in order to represent the user when the new capability, initiative or need is being fleshed out, as well as participation in Integrated Product Teams (IPTs) and across all milestones in the phases of system development and deployment.

For new and innovative designs, developments, or modifications to existing systems, the human factors team must be engaged as soon as possible. One example is a new common Operator Control Panel for all x-ray technology that has obvious aspects and involvement of the human / system interface that drive the requirements process. With this move towards a common graphical user interface for all its equipment, the Agency will see reduced training time and costs, avoid idiosyncrasies between different manufacturers’ interfaces, as well as reduce human error.

Bottle Liquid Scanners and ETD equipment are two more pieces of complicated and sophisticated technology with which the TSO must interface. Physical ergonomics comes into play when considering the size and shape of the wand that collects a trace sample from a passenger’s hands, as well as the specifications for an intense-use x-ray screener chair at the checkpoint.


The next area of concern where human factors is involved is with respect to tools and procedures. An example of the procedures’ question is related to the cognitive task analysis and workload assessment for a new Standard Operational Procedure (SOP) for TSA Pre✓™. This question also queries the impact of the Officer switching between a standard screening lane and a pre-check lane (Pre✓™). In dedicated Pre✓™ lanes, the passenger does not have to divest as many garments or shoes due to new expedited screening benefits. Benefits include leaving on shoes, light outerwear and belts, as
well as leaving laptops and 3-1-1 compliant liquids (LGAs) in carry-on bags.


The checkpoint environment is a noisy, bustling, often space-constrained area where the passengers are not always amenable to the procedures being carried out by the Officers on behalf of TSA. Challenges of operating efficiently and effectively in less than optimal conditions while working to meet TSA’s mission to “protect the Nation’s transportation systems to ensure freedom of movement for people and commerce,” can make for a challenging solution set for the human factors engineers. The job is fast and furious and we are always presented with new and interesting challenges, all while keeping our focus to the future and way forward for this important mission at TSA.


If you travel by air at all, you are aware of changes occurring within the TSA checkpoint screening processes. Most of these are based on risk-based security principles. Application of new intelligence-driven, risk-based screening procedures and enhanced use of technology are combined in
initiatives such as TSA Pre✓™ and Managed Inclusion (MI) with the use of risk assessment enhanced by Passenger Screening Canines and Behavior Detection Officers. MI is being implemented in several airports that currently use TSA Pre✓™. Using additional layers of security to screen the traveler, the passenger steps onto an electronic mat with directional arrows. The mat randomly designates whether the passenger will experience standard or expedited screening through TSA Pre✓™. The human factors team was previously asked to investigate the use of a tablet computer at
the checkpoint to display the designation arrows.

These new initiatives will enhance the experience for the majority of airline passengers who are low risk. This move to increase security by focusing on unknowns, as well as expedite known and trusted travelers, has brought new SOPs and mitigations to the checkpoint. Along with welcome
changes for the passenger, the jobs of the Officers at the checkpoint are also evolving. This brings new human-focused research topics involving hiring, training, performance, assessments, and effective writing and implementation of these new checkpoint procedures. We are fortunate to have
strong leadership support from the top down, and as word of the positive human factors impact on systems requirements or new procedures increases, our team grows in size and diversity of skill sets.


With an eye to the future, the human factors team is working to investigate the feasibility of specialized positions at the checkpoint. The importance and effect of individual characteristics, like attitudes, attributes and aptitudes for either the x-ray operator position or the remaining passenger-focused positions are currently under contract. If psychometric batteries of tests from validated instruments are predictive of performance at the checkpoint for these two positions, the impact to screening, hiring, training, and on-the-job performance, plus the impact to security are obvious.


Since one of the many layers of security includes our TSOs (see Figure 3), the human element is a key factor in the success of many of TSAs initiatives. The human factors engineering team analyzes the human / system interface of new technology and procedures and examines the potential
human-centered impacts and concerns, like increases in cognitive workload, which might accompany these changes.

TSA remains forward thinking and continually establishes multidisciplinary groups to brainstorm ideas that improve operational efficiencies, while enhancing security, developing
new performance metrics, hiring the best person for our Officer workforce, reducing turnover and retraining costs, as well as enhancing passenger experience.

TSA moved from the Department of Transportation to the Department of Homeland Security in 2003 and has a mission to protect the Nation’s transportation systems to ensure freedom of movement for people and commerce. While this paper primarily addresses the Checkpoint at airports, areas of interest and responsibility for the human factors team include checked baggage, cargo and other multi-modalities (i.e. rail). The human factors team at TSA faces a new day, every day with different problems and exciting human-focused questions. The impact human factors makes is real and immediate. Our Officers face a difficult job at our airports. The Agency equips them with excellent training, standardized procedures and cutting edge technology. The airports are fully staffed, trained and hardware is in place. The next decade will mean attention on risk-based security initiatives to improve the passenger experience with no increase in threat to air travel. The human factors team is poised to bring swift solutions and results to support the data-driven decisions the Agency makes.


Figure 1. Travel Document Checker
Figure 2. Checkpoint layout after Travel Document Checker
Figure 3. Layers of Security