Public Transportation Use is Directly Related to More Physical Activity

Background and Purpose Research suggests that public transportation (PT) (e.g., bus, rail) users are more physically active than non-users. However, this difference could be explained by other individual or shared environmental factors that differ between PT users versus non-users (e.g., attitudinal predisposition for being active; transit users live in more walkable neighborhoods and therefore could be walking more for transportation, not necessarily to access PT). Prior studies have not examined whether higher physical activity among PT users is directly attributable to actual PT use, that is getting physical activity through walking to/from their use of PT. Better measures that allow for temporal precision of PT use and related walking can enhance our understanding of how much physical activity, and specifically walking, is directly attributable to PT. This is critical to understanding the potential public health impact of shifts in PT use.

Objectives Through a combination of objective measures of physical activity and reported trips, we examined whether 1) PT users engage in more overall physical activity and specifically time spent walking than non-PT users, 2) whether PT users are more active and walk more on days in which they use PT versus non-PT days, and 3) how much of PT users‘ overall walking and specifically walking on PT days is temporally linked to PT use.

Methods Participants included the baseline sample (n=706; 62% female, 22.3% non-white or Hispanic; $60-69K median household income) of adults from a natural experiment about the impact of a soon-to-open light rail line in the Seattle metropolitan area. Participants were instructed to wear an accelerometer and portable GPS device, and complete a concurrent travel diary, for 7 days. These data were linked by day/time. Physical activity was defined by accelerometry bouts lasting 5+ minutes in which activity counts > 500 per 30-second epoch, while allowing a 2-minute tolerance for sub-threshold counts. Within the physical activity bouts, walking was identified based on GPS speed or recorded walking in the travel diary. PT use was identified in the travel diary. A PT user was defined as an individual recording one or more PT trips during the assessment period. A PT day was defined as any day in which a PT trip or PT place (e.g., bus stop) was recorded. PT-related walking was defined as walking that occurred proximal to (overlapped in time or within a 10 minute buffer around) a recorded PT trip or PT place.

Results Overall, 7.3% of all recorded trips among PT users and non-users were transit trips (n=1921 of 26,270), and 40.4% (n=285) of participants took at least one transit trip during the 7-day assessment period. Among PT users, 45.7% of their days were PT days. Across PT and non-PT days, PT users averaged 46.4 minutes (SD=29.1) of physical activity per day, of which 31.7 minutes (SD=23.1) was walking, and of this 7.2 minutes (SD=8.8) was PT-related walking. Non-PT users averaged 38.4 minutes (SD=33.6) of physical activity per day, of which 21.1 minutes (SD=23.5) was walking. PT users‘ time spent walking that was not PT-related (Mean 24.5; SD=20.3) was similar to non-PT users walking time. When only PT days were considered, PT users engaged in 51.5 minutes (SD=36.4) of overall physical activity, of which 36.2 minutes (SD=28.7) was walking, and of this 14.2 minutes (SD=12.3) was PT-related walking. In contrast, on non-PT days, PT users engaged in only 41.2 (SD=32.6) minutes of physical activity. Walking not related to transit was similar on PT (Mean=22.0; SD=23.3) and non-PT days (Mean=27.0; SD=26.3).

Conclusions Consistent with existing evidence, participants using public transportation were found to be more physically active than non-users. However, there was little difference in average daily physical activity between PT users on non-PT days versus those participants who never used PT. The overall daily physical activity difference between PT users versus non-users was almost wholly attributable to PT users being more active on days in which they took PT, and more specifically to the time spent walking close in time to when they took PT. Indeed, approximately 28% of PT users‘ physical activity and 39.2% of their walking on PT days is temporally linked to using PT. It does not appear that PT users substitute much additional physical activity on non-PT use days for the PT-related walking they do on PT days. These findings suggest that PT use is contributing directly to PT users getting more overall physical activity, rather than there being another factor that explains the relationship between PT use and greater physical activity. Study limitations include the cross-sectional data and the non-representative sample who all had good PT access. More prospective and natural experiment evaluation is needed, but present findings highlight the potential for policies or environmental changes that facilitate more PT use to have a positive public health impact by increasing physical activity.

Support/Funding Source This work was funded by NIH R01 HL091881