Time on task and task load in visual inspection: A four-month field study with X-ray baggage screeners

Area of Science:

• Human Factors
• Cognitive Psychology
• Occupational Safety

Background:

• Vigilance and visual inspection performance are influenced by time on task and task load.
• Current regulations require security screeners to take breaks after 20 minutes of X-ray baggage screening.
• Extending screening durations could alleviate staffing challenges in aviation security.

Purpose of the Study:

• To investigate the impact of extended time on task and varying task loads on screener performance.
• To evaluate the feasibility of increasing X-ray baggage screening durations beyond the current 20-minute limit.

Main Methods:

• A four-month field study was conducted with 22 security screeners at an international airport.
• Screeners inspected X-ray images of cabin baggage for durations up to 60 minutes.
• A control group (N=19) screened for 20 minutes, with task load manipulated (low, average, high).

Main Results:

• Hit rates remained stable for low and average task loads across screening durations.
• Under high task load, screeners increased inspection speed over time, leading to a decreased hit rate.
• Performance degradation was observed specifically at high task loads with prolonged screening times.

Conclusions:

• The findings support the dynamic-allocation resource theory in the context of security screening.
• Extending permitted screening durations to 30 or 40 minutes may be feasible, particularly if task load is managed.
• Optimizing screening protocols requires balancing operational efficiency with sustained performance and safety.