Use of gaze and gait analysis to assess the effect of footway environmental factors on older pedestrians' accessibility
Walking in the footway environment is an essential activity of daily living and the physical activity associated can also improve an individual's quality of life. The possibility and ability for the individual to reach opportunities and participate in activities on foot indicate the accessibility of the footway environment. One of the major hazards in the footway environment that impedes the accessibility is falling. While it may happen to anyone, falling is more common in older people and the consequence of falling could seriously deteriorate their quality of life.
Falls among older people is one of the major public health problems. Fall-induced injuries, either physical or psychological, can lead to further physical frailty and social isolation. Although falls study on the elderly has been widely discussed, there is little information available on risk factors in the outdoor footway environment. The current guidance of design and condition of footway environment, however, is short of scientific justification. The potential hazard of a single step-height, such as defects and kerbs on the pavement, is commonly encountered as well as negotiated by the individual under different lighting conditions. Therefore, a framework within which the interaction among sensory and physical capability and environmental factors could be well investigated is needed.
This thesis investigates the process of planning for negotiating upcoming step-heights on the pavement, and aims at establishing changes in gaze (where people look) and gait (how people walk) behaviour in relation to combinations of environmental factors such as step-heights and lighting levels. About 17 young (aged 25-34) and 17 older (aged 65-74) participants walked on a straight walkway with 16 experimental conditions (8 step-heights at 2 lighting levels, one step-height in each environmental setting), and the visual and walking patterns were collected.
The results demonstrated the inconspicuous descending step-heights (due to a lack of visibility) as well as the lower lighting level demanded additional visual attention and additional time to plan footsteps. Step-height of 60 mm was found to be the threshold of sensory as well as physical capability, which should be considered as suggested guideline for pavement design. Both 125 and 30 mm were perceived as
more dangerous due in part to additional body function requirement and the nature of visual ambiguity respectively.
More importantly, young participants demonstrated the agility and adaptability to different environmental setting whereas older people demonstrated more disturbed gait pattern and increased visual attention. Also, older people were more likely to face the risk of falling as they detected the step-heights later, had shorter time for response than young participants. Therefore in footway design, older people's perception as well as reaction to response to the footway environment should be considered and the pavement should be designed to accommodate their needs.
Bringing together the gaze and gait analysis is proved to be important in this thesis and it is essential for further research in understanding the cognitive process in between. The responses to risks of falling could not be understood without knowing the association between the visual perception and gait adjustments.
The approach developed in this thesis might be used to further analyse microscopic as well as macroscopic scales of accessibility of the footway environment and provide some insights into how the individual's sensory, cognitive and physical capability affect the decision making process while walking.