Maintaining physical activity levels into older adulthood is an important component of healthy aging,(Peel et al., 2005) but urban environments do not always support this. Older adults are more likely than younger adults to have mobility impairments (Ferrucci et al., 2016) and are less likely to drive,(Federal Highway Administration, 2017) and therefore are especially sensitive to neighborhood environmental characteristics (Clarke and Gallagher, 2013; Ghani et al., 2018). Parks can provide infrastructure for older adults to exercise safely and conveniently. However, in the United States, older adults are underrepresented among park users (Evenson et al., 2019), suggesting that neighborhood parks are not adequately serving this population. More evidence is required for planners and policymakers to better design parks for older adult use.

Studies investigating the impact of parks on physical activity among older adults may use either objective or subjective measures of park access, such as proximity to parks (objective) or perceived access to parks (subjective). While objective measures of park access may be more readily translatable to evidence-based policy goals and easier to use in large-scale population health studies, an individual's decision to use a park for exercise is more directly related to their perceived access to parks rather than any external measure (Wan and Shen, 2015). Nor are objective and subjective measurements of park access always closely associated (Boehmer et al., 2006; Larson et al., 2022). Older and lower-income residents can be more likely to have mismatches between perceived and objective environmental measures, (Ball et al., 2008) and residents of deprived neighborhoods that live closer to parks can report less perceived access and less frequent use of parks than do residents of less deprived neighborhoods (Jones et al., 2009). These mismatches may be the result of park characteristics, such as the level of maintenance and the presence of relevant amenities, or neighborhood characteristics, such as greenness and crime. Understanding how park characteristics contribute to perceived access, how perceived access contributes to physical activity levels, and how these relationships operate across different neighborhood contexts, is fundamental to designing interventions to improve park and neighborhood conditions to support physical activity for older adults.

Previous studies have highlighted older adults' park preferences, including the presence and variety of natural features, well-maintained infrastructure and facilities, and the presence of a variety of kinds of parks in the neighborhood (Kou et al., 2021; Wen et al., 2018). Walking paths are frequently cited as important, and older adults may prefer parks that contain a variety of kinds of paths, such as paved and unpaved (Kou et al., 2021) or sloped and flat (Joseph and Zimring, 2007). In addition to park characteristics, neighborhood-level factors including safety and walkability may also influence older adults’ decision to walk or engage in other physical activity outside, (Yen et al., 2014) potentially contributing to park visitation. Older adults who live in proximity to parks with supportive features may be expected to be more physically active as a result of greater park visitation, but characteristics of the surrounding neighborhood may also play a role in this relationship.

Studying the relationship between park characteristics and perceived access is complicated by within-park spatial variation. Considering a large park with exercise equipment close to its eastern border, a resident living near to the western border of the park will have a different exposure to that equipment as a resident who lives near the eastern border. Investigating the role that individual park features play in perceived access requires exposure assessment based on proximity to features themselves, rather than on proximity to parks that contain those features.

In our study setting of Philadelphia, Pennsylvania, USA, park features are available mapped independently of park boundaries. Detailed data is also available in Philadelphia for neighborhood characteristics relevant for older adults’ exercise, including intersection-level crime incidents, the sidewalk network, and the tree canopy. This study spatially links these detailed park and neighborhood data with a subjective measure of perceived park access and self-reported physical activity for a sample of older adults to test the mediational role of perceived park access in the relationship between objective park features and physical activity. We assess whether this relationship varies based on the radius of exposure considered, and test whether model fit is better when considering neighborhood conditions as confounders or as moderators of the relationship between objective park features and perceived park access.