Over half of falls in older adults are caused by tripping. Many of these trips are caused by small obstacles present on outdoor walkways. The current practice for many municipalities is to repair outdoor walkway tripping hazards that are higher than 6mm, ignoring the rest. There is evidence that older adults are likely to trip on obstacles smaller than this cut-off and we hypothesize that lower obstacles may be just as hazardous, if not more hazardous, for older adults (who tend to have lower foot clearances) because smaller obstacles may be more difficult to see. The existing evidence reporting foot clearance of younger and older adults include only lab-based measurement, many measure foot clearances from participants walking on a treadmill. There are no existing studies that report on measurement of foot clearance of real-world pedestrians.
To address this gap, our team recently developed a device for measuring foot clearance on outdoor walkways we call the Parallel Laser Array Recording device (PLAR), shown below. The device is designed to be positioned at ground level next to a public walkway to collect video images of a pedestrian’s lower body as he or she walks by. The PLAR includes two calibrated parallel laser beams positioned within the field of view of the video camera such that they are projected onto the pedestrian’s lower leg. The known distance between these beams is used as a scale on the video image to estimate foot clearance distances.
The benefits of this system are that it can easily collect large amounts of video data quickly from many pedestrians. We are currently developing an automated method to speed up the processing of this data using computer vision and machine learning techniques.