Body Scanning Technology: An Early Human Factors Analysis

Celine Lilliane Aurore Jacques Human Performance Solutions

QinetiQ Farnborough, Hampshire

CLAJACQUES@QinetiQ.COM

Abstract— In March 2009, QinetiQ conducted an Early Human Factors Analysis (EHFA) on behalf of the UK Department for Transport (DfT) for the implementation of body scanning technology in the airport security screening context. EHFA is a well-established technique, used extensively as part of UK Ministry of Defence (MoD) acquisition [10]. This was the first time EHFA was used in the security domain. The aim of EHFA is to provide an early indication of where key Human Factors (HF) issues and risks associated with body scanners lie so that mitigation strategies can be developed. EHFA is structured around seven Human Factors Domains ranging from Manpower and Training to System Safety and Human Factors Engineering.

The first stage of the EHFA was to collect baseline information. Journal research, system evaluations, and public sources were collated to produce a full picture of the identified six body scanning methodologies: walk-through metal detectors, pat-down searching, backscatter X-ray imaging, walk-through and non-walk-through millimetre wave and air. The second stage of the EHFA was a triage analysis, which produced a high level assessment of the baseline data and an early indication of potentially problematic areas. The triage revealed that Manpower, Personnel, System Safety, and Social and Organisational HF issues were high priority areas for further investigation.

The third stage of the EHFA was to identify and quantify specific HF issues associated with each methodology. Issues were quantified according to their impact and likelihood, which were combined to give an overall score. Fifty nine issues were yielded; 73% of the issues were of medium to high priority highlighting a large number of areas where HF issues could occur.

The final stage of the EHFA was to develop mitigation strategies for the high priority issues. Mitigation strategies were devised for the 29 highest priority issues. Mitigation strategies were recommended based on research in the aviation security domain and on human factors integration best practice. The mitigation strategies involve the application of a Best Practice Model (BPM) for the selection and management of staff, based on Job Analysis of the body scanning task. Separate mitigation strategies were developed for issues not addressed by the BPM, namely those concerning safety and human factors engineering.

This research successfully applied for the first time in a security domain the EHFA methodology, proposing a mitigation approach that if implemented appropriately will lead to effective

use of body scanning systems. The compatibility of the EHFA process with body scanning methodologies points towards the technique being applied to other systems and technology in security research in the future.

Keywords- Early Human Factors Analysis, Body scanning technology, airport security, Human Factors, Mitigation strategies

I. INTRODUCTION This paper documents the conduct of an Early Human

Factors Analysis (EHFA) undertaken for the implementation of Body scanning technology in airport security environments. The EHFA identifies and assesses the human-related risks associated with the use of the technology to allow mitigation strategies to be developed.

The study was conducted on behalf of the UK Department for Transport.

Body scanning technologies are used to detect threats carried on the person. They scan for organic and inorganic objects concealed on the outside of the body. Used as a security measure in airport environments, they are relied upon to both quickly and effectively identify whether a passenger is carrying a threat, and help identify what that threat is. There are a variety of body scanning techniques on the market today falling into six main categories:

1. walk-through metal detectors; 2. pat-down searches; 3. backscatter X-ray imaging; 4. walk-through millimetre-wave; 5. non-walk-through millimetre-wave and 6. air.

As yet, there has been limited work in the aviation security domain to collate and understand the Human Factors (HF) issues associated with body scanning technology. It is imperative that associated HF issues are identified so that they can be subjected to analysis and the development of mitigation strategy. The conduct of an EHFA will ensure that these technologies can be introduced and implemented with optimum utility, efficiency, and safety.

This work has been undertaken to provide a preliminary indication of where the key HF issues lie by following a process known as EHFA. The aim of this work is to identify

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the HF issues that need to be addressed to ensure that the introduction of body scanning technologies supports the Security Officer task.

EHFA is a methodology that enables decisions to be traceable, highlights issues, and specifies what can be done to mitigate them. It is a well-established technique, originally developed for the MoD Human Factors Integration (HFI) process. HFI provides a process that ensures the application of scientific knowledge about human characteristics through the specification, design, and evaluation of systems. HFI is based on a framework of seven domains as shown in table I.

TABLE I. HUMAN FACTORS DOMAINS DEFINITIONS

HF Domain Definition Manpower the number of personnel required to operate, and train

for using the system Personnel the physical and cognitive capabilities necessary to

achieve system performance Training the methods used to develop and maintain the

required knowledge, skill, and abilities to operate the system

Human factors engineering

integration of the physical and cognitive characteristics of users into system design

Health Hazard Assessment

the short and long term hazards to health resulting from normal operation of the system

System safety the risks that occur when the system is functioning in an abnormal manner

Social and Organisational

the application of organisational psychology and information science principles to address the impact of introducing new equipment into complex organisations

The EHFA process is divided into the following sub-tasks:

• baselining;

• triage analysis;

• elicitation of HF issues and

• development of mitigation strategies.

This paper provides a description of the conduct and findings for each of the sub-tasks followed by the recommendations made and conclusion.

II. BASELINING The baseline is the initial set of information that best

describes the product or operation in question as known at the time. The baseline is analysed to identify those areas that may give cause for concern from a human factors perspective. Baseline information for this project was gathered by searching academic journals on the internet, consulting manufacturer materials and liaising with key body scanning technology knowledge holders. From the baseline data set the body scanner models were grouped and six categories identified.

The first is walk-through metal detectors; a mobile stand alone archway that passengers are required to walk through. An audible alarm is sounded if metal is detected and a red light indicates on what area of the body it is. Research has shown that walk-through metal detectors have been regarded positively by the staff using them. Some reported difficulty in

using the machines [6]. The second is pat-down searches, involving manual searching of a passenger’s outer body. Male Security Officers search male passengers and vice versa for females. Research has shown there to be varied performance of searching across different body areas and between screeners [3].

The third is backscatter X-ray imaging. A single high energy X-ray is passed over a passenger’s body. High density objects, such as guns and knives, absorb the X-ray and are shown as dark on the image produced. Passengers stand in front of the scanner in three different positions and an image of each is sent to a screener that is removed from the location of scanning. Within the baseline data set there was little consensus on the health dangers involved. In an operational trial, 73.2% passengers were happy with the health and safety risks and 89.7% felt comfortable with their image being viewed [1].

The fourth is walk-through millimetre-wave. High frequency radio waves are reflected off of the passengers’ bodies to make an image in which one can see anything hidden under the clothes [9]. The passenger is asked to adopt two different positions and these images are sent to a remote monitor. In an operational trial 85% public who agreed to use the scanner were confident that the scanner would improve security at the airport and only 15% said they prefer pat-down searches [4].

The fifth is non-walk-through millimetre-wave. Using the same technology as the fourth category, this stand-off form does not require passengers to walk through any structure. The technology scans for differences in density on a person’s body. Security Officers can work closely with a behavior detection expert team to focus on a particular individual who has been deemed as suspicious. The sixth and final category is air. Gentle puffs of air dislodge particles on the body, clothing and shoes of the passenger. Particles are analysed for traces of narcotics and explosives in comparison to a database of over 40. Research has shown this technology to be positively regarded by passengers and staff alike [5].

III. TRIAGE ANALYSIS The triage analysis stage involves high level assessment of

the baseline data to provide an early indication of potentially problematic areas and to prioritise the human factors resource effort throughout the EHFA. A workshop was held to conduct the triage analysis. In attendance were human factors specialists, occupational psychologists, and aviation security experts. Attendees were presented with an outline of the EHFA methodology and the baseline data. In alignment with MoD EHFA guidelines [10], each of the seven Human Factors (HF) domains were assessed, according to each body scanning category’s potential impact in that area. Potential HF issues were discussed in each area and then on the basis of that information as a whole, a rating was given. Potential impact was scored as high, medium, or low according to the categorisation in Table II.

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TABLE II. CATEGORIES OF IMPACT

Impact during

assessment period

Descriptions of impact in relation to HFI

High The issues highlighted prevent the system achieving specified performance

Medium The issues highlighted prevent the system achieving specified performance but can be managed within system margins.

Low The issues highlighted are within performance margin for system.

High potential impact HF domains were Manpower, Personnel, System Safety, and Social and Organisational. High potential impact body scanning technologies were pat-down searches, backscatter X-ray imaging, and walk-through millimetre-wave scanning.

In the face of incomplete data, certain assumptions were made and abided to throughout the triage analysis stage and thereafter (such as “Passengers are not told they are being scanned with non-walk-through millimetre-wave technology”). These were logged in the Assumptions Register.

The triage analysis is intentionally high level and is limited by the availability of a baseline data set. It is therefore important to highlight some caveats on the assessment that was made.

Firstly, limited information is known about the maintenance requirements of these technologies. Therefore, HF issues associated with maintenance tasks were not considered during analyses. Second, considerations of each technology focused up until the point of alarm detection, not further into alarm resolution. Third, each scanning technology was assessed singularly, outside of the system in which it would sit (for example, walk-through metal detectors and non-walk-through millimetre-wave scanners are followed commonly by pat-down searching or backscatter X-ray and walk-through millimetre-wave scanning to resolve the detection).

IV. ELICITATION OF HF ISSUES Following the triage analysis, specific issues are

categorised, quantified, and prioritised, to produce the key outputs of the EHFA. A HF Issues log was compiled containing the issues discussed within the triage analysis workshop as well as novel issues gleaned from further investigation and reflection upon the seven HF domains.

This HF Issues log was then distributed to the workshop team for review. A second workshop was held where the issues were reviewed, amended, added to, and omitted as necessary.

During the workshop, each issue was quantified and scored for impact (Table IIII), and likelihood of occurrence (Table IV). These ratings were then combined to give each issue an issue likelihood-impact score, using the categorisation in Table V.

TABLE III. CATEGORIES OF IMPACT

Impact during

assessment period

Descriptions of impact in relation to HFI

High The issues highlighted prevent the system achieving specified performance

Medium The issues highlighted prevent the system achieving specified performance but can be managed within system margins.

Low The issues highlighted are within performance margin for system.

TABLE IV. CATEGORIES OF LIKELIHOOD

Likelihood of occurrence

Confidence in information on which cause is based

High The issues highlighted are likely to be encountered each time activity is conducted.

Medium The issues highlighted are likely to occur sometimes

Low The issues highlighted are unlikely/may exceptionally occur.

TABLE V. ISSUES LIKELIHOOD-IMPACT SCORE MATRIX

Impact

Likelihood of occurrence

High Medium Low

High 6 5 2

Medium 5 4 1

Low 4 3 1

The HF Issues and their scores were logged in the HF issues log, documenting each HF issue and the HF domain and body scanning technology that it is aligned to. Each HF issue was given a unique number. The HF issue log represents the main output from this stage of the analysis. The high scoring issues (rated using the method in Table V) tended to be concerned with:

• attraction, selection, and retention of personnel;

• training of personnel;

• organisation, allocation, and distribution of tasks and shifts;

• workspace allocated to personnel;

• health and safety of personnel; and

• reliability of the technology.

System Safety and Social and Organisational domains were those with the highest number of HF issues. This is due to the fact that acceptability and trust of the technologies is likely to present an issue. Likewise, with new technologies, it can be difficult to outline the potential health and safety risks of abnormal operation, namely because they have not been in operation before. During the triage analysis stage, these two HF domains were rated as high priority domains to investigate.

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The technology type with the highest number of HF issues is the backscatter X-ray imaging. This is due to their use of X-ray beams. In close succession is walk-through millimetre-wave, which has many of the same risks as the backscatter X-ray. Considerably fewer issues were identified for walk-through metal detectors. This is likely to be due to the simplicity of the technology compared to others, but perhaps more importantly due to the fact that walk-through metal detectors are already being used in airports and Security Officers and passengers alike are familiar with them. Interestingly however, pat-down searching still raised a large number of issues despite it also being used extensively.

The majority of issues (49%) were scored as a “four” or a “five”. 17% had the highest rating of six. This results in 73% of the issues being rated as four, five, or six. This points towards there being a substantial number of areas that need further investigation and/or mitigation.

V. MITGIATION STRATEGIES The final stage of the EHFA is to develop mitigation

strategies for the high priority HF issues that have been identified and recorded in the HF issues log. High priority HF issues were identified as those having been awarded a six (high impact and high likelihood of occurrence) or a 5 (high impact and medium likelihood or medium impact and high likelihood). This identified 29 HF issues rated as a 5 or a 6 for which mitigation strategies were developed. The issues being scored as a four were reviewed and it was felt that either they were of markedly lower priority, or that the mitigating strategies developed for issues scoring five or six would actually mitigate some of the issues scoring four as well.

Mitigation strategies were developed using the MOD: Defence Standard 00-025: Human Factors for designers of systems, past research in the aviation security domain, Human Factors Integration best practice, and knowledge and experience of the aviation security domain.

Mitigation strategies fell under two streams; one for pat-down searching and one for body scanning technology. This distinction arises because pat-down searching is a significantly different type of scanning from the others and also represents as a comparison to more novel processes. The key approach for mitigation is the application of a Best Practice Model (BPM) [10] for the selection and management of staff. This model outlines how it is essential for any selection, training, and performance assessment to be based upon accurate descriptions of the knowledge, skills, and abilities required for the job in question. To mitigate other issues that are not covered by the BPM, namely those concerning safety and/or human factors engineering, separate mitigation strategies were developed.

A number of possible mitigation strategies were outlined to overcome the high priority risks that were identified.

VI. RECOMMENDATIONS MADE The EHFA process identified a number of high priority

issues and mitigation strategies have been developed to address them.

It is recommended that the mitigation strategies are employed in four stages of work to ensure important risks are addressed first and that potentially useful information or output from one strategy is useable for another.

The first task is to identify the specific requirements that need to be made of manufacturers who are developing and selling the body scanning technology. It has been identified that to avoid risks to operability, usability, performance and safety, manufacturers should have conducted certain activities.

The second stage in mitigating the high priority HF issues involves conducting research. There are various subsets to this research, however, and an intuitive order in which to carry it out. The first is to conduct research concerning pat-down searching, the second is to conduct literature reviews in a number of areas, the third is qualitative research and the fourth is research once technology is in operational trial or has been deployed.

The third stage involves making use of the information and guidelines from manufacturers, coupled with findings from research, to deliver useful guidance documentation to airports.

Finally, in order to maintain efficient operation it is recommended that Security Officer and scanner performance is assessed regularly, according to the BPM. This will indicate whether processes are working optimally.

This four stage mitigation programme should ensure that body scanning technology is introduced in a safe, effective, and manageable way. This mitigation approach should be viewed as flexible and should be refined and tailored in line with customer needs and the wider strategy for deployment of body scanners in the UK.

VII. CONCLUSIONS The EHFA process has successfully and appropriately

allowed expert input into decisions that are traceable. The methodology has proved compatible with the assessment of the baseline data and has yielded 73% of issues being rated as a score of four, five or six (medium to high priority). This points towards a significant number of issues to be considered in order for body scanning technology to be implemented appropriately and to maximum benefit.

This research successfully applied for the first time in a security domain the EHFA methodology, proposing a mitigation approach that if implemented appropriately will lead to effective use of body scanning systems. The compatibility of the EHFA process with body scanning methodologies points towards the technique being applied to other systems and technology in security research in the future.

ACKNOWLEDGMENT Thanks to the following colleagues who contributed

towards the workshops and report of this work: Vicky Cutler, Martin Thody, Eva Koritsas, Stephanie Appleyard, and Christine D’Silva.

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