Abstract
This paper presents the first study quantifying how practitioner experience affects perceived quality and usability of compressed Forward-Facing Video (FFV). We captured a bespoke 8K UHD forward-facing dataset and encoded each sequence using H.264/AVC and HEVC at three bitrates (30, 50, and 60 Mbps). 18 rail practitioners were recruited and stratified by operational experience. Participants provided subjective ratings of video quality and usability and completed a task-based recognition assessment with associated decision-confidence ratings. FFV is increasingly integral to railway safety assurance and incident investigation, providing visual evidence for events such as Signals Passed at Danger (SPAD), near-misses, and collisions. In operational deployments, FFV acts as a human-in-the-loop decision-support resource that must be transmitted and archived under bandwidth and storage constraints, making compression unavoidable. However, compression artefacts can reduce the visibility of decision-critical cues and potentially undermine confidence in operational judgements. While expertise has been shown to shape video interpretation in medical and surveillance contexts, its influence on rail FFV interpretation has received limited empirical attention. Initial results indicate a clear effect of experience: more experienced practitioners appeared more tolerant of visible artefacts, rated compressed FFV as more usable, and reported higher confidence when making task judgements under degraded conditions. A three-way mixed-design ANOVA confirmed a significant effect of experience, while codec and bitrate effects were non-significant, with performance approaching a ceiling at 60 Mbps. These preliminary findings motivate practitioner-aware evaluation protocols and system requirements for safety-critical rail FFV, complementing fidelity metrics with interpretability-driven acceptance criteria. We outline implications for codec selection, bitrate provisioning, and role-based quality thresholds in railway video systems engineering.