摘要：Objectives. We assessed effects on physical activity (PA) and weight among participants in a complete street intervention that extended a light-rail line in Salt Lake City, Utah. Methods. Participants in the Moving Across Places Study resided within 2 kilometers of the new line. They wore accelerometers and global positioning system (GPS) loggers for 1 week before and after rail construction. Regression analyses compared change scores of participants who never rode transit with continuing, former, and new riders, after adjustment for control variables (total n = 537). Results. New riders had significantly more accelerometer-measured counts per minute than never-riders ( P < .01), and former riders had significantly fewer ( P < .01). New riders lost ( P < .05) and former riders gained ( P < .01) weight. Former riders lost 6.4 minutes of moderate-to-vigorous PA (MVPA) per 10 hours of accelerometer wear ( P < .01) and gained 16.4 minutes of sedentary time ( P < .01). New riders gained 4.2 MVPA minutes ( P < .05) and lost 12.8 ( P < .05) sedentary minutes per 10 hours accelerometer wear. Conclusions. In light of the health benefits of transit ridership in the complete street area, research should address how to encourage more sustained ridership. Historically, many streets have been engineered to support speedy car travel, with designs that manifest little concern for other users, such as pedestrians or transit riders. 1 Reflecting a cultural shift in priorities, public health advocates in the United States 2 and other countries 3 are supporting transportation policies and built environment interventions that enhance opportunities for physical activity (PA). Complete street policies support roadways designed or altered to accommodate active transport by pedestrians, cyclists, or transit users. Physical environment modifications created by such policies vary substantially in scale, from the addition of painted bike lanes to the installation of new rail lines. Complete street policies were the most frequently sought policies by 59 active-living collaborative groups, 4 have been endorsed by the Centers for Disease Control and Prevention, 5 and have been adopted by more than 600 jurisdictions. 6 However, research on complete streets often focuses on the notable challenges of implementation, 7,8 rather than on assessment of potential health effects. 9 Past research showed that transit riders self-report more PA and healthier body mass indexes (BMIs). A round trip on transit typically involves 4 walks or bike rides to get to and from the transit stop, 10 making transit use a form of active transportation. A review of mostly cross-sectional studies worldwide found 9 studies that showed that transit use was associated with between 8 and 33 minutes of PA per day of transit use 11 ; 4 of these were limited to self-reported PA. 12–15 In the United States, according to the 2001 National Household Travel Survey, the 3312 transit riders reported walking 19 minutes daily to and from transit 12 ; similar results emerged from more recent waves of this survey. 16 Important advances in research are the use of objective measures of PA and BMI in longitudinal designs. Indeed, objective measures of PA have yielded weaker associations with built environment features than were found by studies relying on self-reports, according to a recent review. 17 Still, in cross-sectional studies, transit use was correlated with more pedometer-measured PA. 18,19 Transit commuters in Seattle, Washington, and Baltimore, Maryland, achieved 4 to 8 more moderate minutes (with a threshold of 1952 counts per minute [cpm]) of accelerometer-measured activity daily than noncommuters. 20 A more recent Seattle study used travel diaries and accelerometers to relate reported transit use to moderate PA (defined as ≥ 5-minute bouts of ≥ 1000 cpm). 21 Participants who recorded occasional to frequent diary-logged transit trips accrued 2.3 to 15 more daily minutes of walking (defined as traveling 2–6 km/hour, according to global positioning system [GPS] measures) than did nontransit users. 22 Longitudinal studies show that an increase in transit use correlates with better health measures. Phone surveys before and after a Charlotte, North Carolina, rail opening revealed that those who became daily rail riders (n = 26) reported their BMI as 1.18 points lower than that of nonrail commuters (n = 275) and were 81% less likely to become obese, although they did not report a greater likelihood of attaining 150 minutes of walking per week. 15 Residents who started using a new Salt Lake City, Utah, rail stop had more accelerometer-measured occurrences of moderate-to-vigorous PA (MVPA) than nonusers, and fewer were obese. 23 The addition of the new stop was associated with an 18.75% increase in the number of residents who reported using light rail, and new riders increased their MVPA. 10 Yet no study has verified ridership by using GPS data to confirm transit location, verified PA with accelerometry data, and provided clinically obtained BMI measures. We aimed to fill this gap. Tracking PA before and after complete street “natural interventions” can provide quasi-experimental evidence of behavior changes. 9 Although not all the intended consequences of a complete street makeover, such as residential and commercial development, will be evident immediately, changes to active travel patterns may be detectible early. We examined objective PA, verified by accelerometry data, and clinically measured BMI changes that accompanied transit ridership changes along a complete street implementation in Salt Lake City that provided 5 new TRAX light-rail neighborhood stops. GPS measures to confirm transit ridership are needed because studies have found more walking 24,25 or lower weight 26 associated with residential proximity to transit stops, which may reflect the location of some transit stops in pedestrian-friendly, transit-oriented developments. 27 Generally, pedestrian-friendly designs provide at least moderate population densities and a variety of desirable destinations, supported by well-connected street designs. 28,29 We therefore used GPS data to ensure that residents were in fact using transit in the complete street corridor. We hypothesized that residents who started to use the new complete street intervention area for transit would engage in more PA and have less BMI increase than other residents and that conversely, any residents who stopped using the corridor for transit should accrue less PA and gain weight.
