Primary exposure

Density of neighborhood public transit stops within participant’s census tract was obtained from the National Neighborhood Data Archive [21]. The National Neighborhood Data Archive calculates density of neighborhood public transit stops within each census tract in the United States using data from the National Transit Map (NTM). NTM compiles General Transit Feed Specification data provided by 270 regional transit authorities in the United States and is continually updated by participating agencies [22]. The 270 participating regional transit authorities represented in the NTM dataset includes static information on locations where fixed-guideway and fixed-route pick up and drop off riders (i.e., transit stops). Stops within the NTM dataset include various modes of public transport (e.g., bus, subway, rail) available. Number of neighborhood transit stops in 2018 were captured and aggregated by researchers in April 2019 [21]. Density of neighborhood transit stops were calculated per square mile within 2010 census tract boundaries. Density of neighborhood transit stops was categorized into three groups: no transit stops documented, at least one transit stop and less than 10 transit stops per square mile, and greater than 10 transit stops per square mile.

Walking for exercise was measured during the annual interview using self-report by asking participants whether they ever walked for exercise in the last month. A binary response of ‘Yes’ or ‘No’ was recorded.

Individual public transit use was self-reported by participants during the annual interview. Participants were asked “In the last month, how did you get to places outside your home? Did you take public transportation (the bus, subway, or train)?” Participants provided a binary response of ‘Yes’ or ‘No’.