How do terrain gradients and route detours impact travel mode choices among older adults?

Ensuring the mobility and travel of older adults is essential for maintaining their quality of life and promoting sustainable social development. Mountainous cities, with their undulating terrain and steep slopes, present significant challenges in providing adequate and equitable travel environments for older adults. However, research on the elderly travel behavior in such topographically challenging cities is relatively limited, and the influence of topography on their mode choice remains under-explored. This study employs a Multinomial Logit (MNL) model to investigate the mode-specific influence of terrain gradients and route detours on choice behavior of older adults, utilizing 2021 resident travel survey data from Guiyang, a representative mountainous city in China. The results indicate that these topographic characteristics significantly enhance the explanatory power of the elderly travel behavior model. Specifically, route detours have a more sensitive and significant impact on elderly choice of travel mode than terrain gradients. Older adults are more likely to walk uphill sections to complete a trip, and the influence of gentle and steep slopes on different modes of travel varied significantly. Furthermore, the study also examines how built environment and socio-demographic factors influence elderly travel, offering insights for developing age-friendly urban environments in similarly complex terrains.