Riz à Porta, Robin
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Night work, circadian rhythm, and cognitive performance: A field study with airport security screeners
Gibt es Threat-Image-Projection-Artefakte bei Luftsicherheitskontrollen mit Röntgengeräten? Eine erste Ratingstudie
Threat-Image-Projection (TIP) ist eine weitverbreitete Software-Applikation für Röntgenmaschinen, die bei Sicherheitskontrollen an Flughäfen eingesetzt werden. Während der Sicherheitskontrolle projiziert TIP in Echtzeit zuvor aufgenommene Bilder von verbotenen Gegenständen (engl. fictional threat images, FTIs, hauptsächlich Pistolen, Messer und Bomben) in Röntgenbilder von Passagiergepäck. TIP wird eingesetzt, um die Aufmerksamkeit des Sicherheitspersonals (Screener) zu erhöhen, ihre Arbeit interessanter zu gestalten und ihre Erkennungsleistung zu überprüfen. Hierzu sollten die projizierten FTIs nicht von echten Gegenständen unterscheidbar sein, also nicht durch Projektionsartefakte erkannt werden können. Diese Studie hatte zum Ziel, TIP-Bilder auf solche Artefakte hin zu untersuchen. Als Erstes wurden Interviews mit Screenern durchgeführt, bei denen sie nach Artefakten befragt wurden, die ihnen im Berufsalltag auffallen. In einer zweiten Studie haben Screener 600 TIP-Bilder zu Artefakten und der allgemeinen Qualität bewertet. Jedes Bild wurde mindestens von 12 Screenern bewertet. Der grösste Teil der Bilder (80%) wurde als insgesamt realistisch bewertet. Am häufigsten als unrealistisch eingeschätzt wurden die Ausrichtung des FTIs im Vergleich zum übrigen Gepäcksinhalt und die Positionierung, bei welcher die FTIs teilweise andere Objekte zu durchdringen scheinen.
How realistic is threat image projection for X-ray baggage screening?
At airports, security officers (screeners) inspect X-ray images of passenger baggage in order to prevent threat items (bombs, guns, knives, etc.) from being brought onto an aircraft. Because threat items rarely occur, many airports use a threat-image-projection (TIP) system, which projects pre-recorded X-ray images of threat items onto some of the X-ray baggage images in order to improve the threat detection of screeners. TIP is regulatorily mandated in many countries and is also used to identify officers with insufficient threat-detection performance. However, TIP images sometimes look unrealistic because of artifacts and unrealistic scenarios, which could reduce the efficacy of TIP. Screeners rated a representative sample of TIP images regarding artifacts identified in a pre-study. We also evaluated whether specific image characteristics affect the occurrence rate of artifacts. 24% of the TIP images were rated to display artifacts and 26% to depict unrealistic scenarios, with 34% showing at least one of the two. With two-thirds of the TIP images having been perceived as realistic, we argue that TIP still serves its purpose, but artifacts and unrealistic scenarios should be reduced. Recommendations on how to improve the efficacy of TIP by considering image characteristics are provided.
Examining Threat Image Projection Artifacts and Related Issues: A Rating Study
Threat image projection (TIP) is a widely used software function of X-ray machines at airport security checkpoints. TIP projects fictional threat images (FTIs) of actual pre-recorded threat items (mainly guns, knives and improvised explosive devices) into the X-ray images of passenger baggage before they are displayed to security officers (screeners) for screening. TIP increases attention and motivation of screeners and is often used to measure their detection performance. In order to be effective, TIP has to project FTIs in a realistic way. In other words, it should not be possible to detect FTIs by simply detecting visual artifacts resulting from TIP projection. This study was conducted to evaluate TIP quality regarding potential artifacts. First, we interviewed screeners to explore which TIP artifacts they encounter in their day-to-day work. In a second step, we conducted a rating study to quantify the identified artifacts and the quality of TIP images in general. The majority of images (80%) produced by TIP were judged by screeners to appear realistic. However, in some images FTIs were positioned inadequately: the alignment (compared to the surrounding baggage items) appeared artificial (15%) or the placement appeared physically implausible (17%; e.g. an improvised explosive device going through a heel). These two issues also significantly affected the image to appear unrealistic in general. We conclude that in most cases, TIP succeeds in projecting FTIs without creating discernable artifacts. In some cases however, the FTI is positioned inadequately, which could be improved in the future.