Developing an equitable slow traffic system is essential for elderly well-being amid global population aging. Using Shenzhen, a rapidly aging city, this study constructs two different walking speed scenarios (Standard: 5 km/h vs. Elderly: 2.7 km/h) to assess the slow traffic system accessibility based on Worldpop data and the OSM road network. The study further explores spatial and temporal changes in the underserved elderly population and associated influencing factors. The results indicate: (1) In 2020, 15-minute accessibility to essential infrastructure was 68.25% (Standard) versus 24.27% (Elderly). Spatial compatibility between the system and elderly distribution is very limited. (2) From 2020 to 2035, as Shenzhen ages, the underserved elderly population is projected to increase from 403,069 to 1,545,146. The growth rate of the underserved elderly exceeds that of the total elderly population, exacerbating inequity. (3) POI variety is the most important factor affecting accessibility. It is negatively correlated with poor accessibility; consequently, increasing infrastructure diversity can improve accessibility. Furthermore, the impact of dynamic population growth exceeds the static population base, exhibiting intense spatial fluctuations. Areas with a positive coefficient for this factor face simultaneous population pressure and service deficits, requiring urgent attention. This study reveals the dynamic relationship between elderly population growth and slow traffic system in rapidly aging areas. The results provide a scientific reference for infrastructure planning and policy formulation in Shenzhen and other similar cities experiencing rapid aging.

Slow traffic system, Rapidly Population aging, scenario analysis, Infrastructure equity