Dynamic analysis of firefighter movement in single-file experiment at different visibility levels

Firefighter casualties frequently occur in low-visibility environments, such as fire scenes filled with smoke. To study the influence of visibility on the movement characteristics of firefighters' longitudinal movement, we conducted a single-file experiment under four visibility conditions. The study found that under different visibility conditions, firefighters exhibited four types of movement behaviors, including independent movement, assisting movement, exploring movement, and connecting movement, leading to distinct movement characteristics. Under invisible conditions, independent movement behavior was no longer observed. At high densities (N > 20), connecting movement accounted for more than 60 %. When Light transmittance (LT) = 100 %, 0.2 %, and 0.1 %, the influence of visibility on the movement characteristics of firefighters, such as velocity and headway-velocity relationship, was largely consistent with that of pedestrians. However, influenced by daily training requirements and rescue experience, firefighters exhibited more active body movements in dark environments (LT = 0 %). This behavioral movement significantly weakened the stop-go wave phenomenon, resulting in smaller lateral sway amplitudes that mitigated the adverse effects of density on movement. Furthermore, the adaptation time was notably shorter, with a critical headway of only 0.88 m. This study represents an initial attempt to explore the single-file movement characteristics of firefighters. The empirical data provided can serve as a foundation for modeling and further guide training and rescue missions for firefighters in low-visibility fire environments.