Identify Stress Location during Low-Speed Mobility Travel Using Environmental Data

In Japan, low-speed mobility devices (LMDs), such as electric wheelchairs and mobility scooters, are increasingly used to support mobility for older adults and individuals with mobility difficulties. However, during outdoor travel, environmental factors including uneven road surfaces, crowded pedestrian spaces, and narrow sidewalks can impose psychological stress on users and hinder continued LMD use. Identifying locations where stress is likely to occur is therefore important for improving travel comfort and safety. This study proposes a method for identifying stress locations based on environmental data during LMD travel by introducing a Composite Stress Score (CSS) that integrates multiple LMD-specific stress factors. Post-ride questionnaires identified three primary stress factors: poor road surface/vibrations, encounters with others, and narrow sidewalks. These factors were quantified using vertical acceleration, encounter counts derived from onboard video recordings, and sidewalk width, respectively, and stress levels were estimated for 100-m route segments. The relationship between CSS-based stress estimation and physiological stress responses was evaluated using heart rate variability (HRV) indexes. The results show that combining multiple environmental stress factors yields stronger associations with physiological stress responses, and segments classified as high-stress exhibited significantly lower SDNN values. These findings demonstrate the potential of the proposed method to identify stress locations during LMD travel using environmental data.