We use panel data to investigate the before-and-after impact of a new light rail transit line on active travel behavior. Participants were divided into a treatment group and a control group (residing < ½ mile and > ½ mile from a new light rail transit station, respectively). Self-reported walking (n=204) and accelerometermeasured physical activity (n=73) were obtained for both groups before and after the new light rail transit opened. This is the first application of an experimental-control group study design around light rail in California, and one of the first in the U.S. Our panel design provides an opportunity for stronger causal inference than is possible in the much more common study designs that use cross-sectional data. It also provides an opportunity to examine how an individual's previous activity behavior moderates the role that new light rail transit access plays in promoting active travel behavior. The results show that, when not controlling for subject's before-opening walking or physical activity, there was no significant relationship between treatment group status and after-opening walking or physical activity. However, when controlling for an interaction between baseline walking/physical activity and treatment group membership, we found that living within a half-mile of a transit station was associated with an increase in walking and physical activity for participants who had previously low walking and physical activity levels. The results were opposite for participants with previously high walking and physical activity levels. Future policy and research should consider the possibility that sedentary populations may be more responsive to new transit investments, and more targeted approaches in transit service would be needed to encourage people to make healthy travel choices.

This study examines the moderating effect of perceived safety on the association of green space with neighborhood social capital in older adults. Green space may play an important role for promoting neighborhood social capital and health for older adults; however, safety remains a significant challenge in maximizing the benefits of green space. Data were drawn from 647 independent-living seniors who participated in the Senior Neighborhood Quality of Life Study in the Seattle/King County and Baltimore/Washington DC region. The results suggest that certain green space elements, such as natural sights, may be beneficial to neighborhood social capital of older adults. However, other types of green space, such as parks and street trees, may be less advantageous to older adults who perceive their neighborhoods as unsafe for pedestrians. Findings highlight the importance of pedestrian safety in examining associations of green space with neighborhood social capital in older adults. Further studies using a longitudinal design are warranted to confirm the causality of the findings.

Studies of the built environment and physical activity (PA) have primarily been cross-sectional. Evidence on the causal impacts of transportation improvements on PA and sedentary behavior (SB) is lacking. This study assessed the effect of retrofitting an urban greenway on PA and SB in Vancouver, Canada. A sample of 524 participants (median age of 44; 57% female) were divided into experimental and control groups, and the effect of exposure to the greenway was examined by using different distance thresholds. Self-report measures of moderate-to-vigorous PA (MVPA) and SB were collected using the International Physical Activity Questionnaire (IPAQ-SF) before (baseline; 2012-2013) and after (follow-up; 2014-2015) construction of the Comox-Helmcken Greenway in 2013. Mixed-effects models estimated the impacts of greenway on MVPA and SB. For participants living near the greenway (≤ 300m), the odds of achieving an average of 20 minutes of daily MVPA doubled (OR=2.00; 95% CI=1.00, 3.98) after the greenway's opening. The odds of being sedentary for more than 9 hours declined by 54% (OR=0.46; 95% CI=0.25, 0.85; p < 0.01) after opening. PA benefits from the greenway declined with distance from 100 meters to 500 meters. Reduction in SB was lowest at 100 meters and greatest at 300 meters. Retrofitting an urban residential neighborhood through greenway intervention can be successful in promoting physical activity while reducing sedentary behavior. Recommendations for future longitudinal research include the use of objective PA measures, studying different neighborhood contexts, collecting more representative samples, and minimizing attrition. Highlights:  A pre-post evaluation of urban greenway on physical activity and sedentary behavior  Participants near the greenway doubled their odds of achieving 20 minutes daily MVPA  The odds of being sedentary for more than 9 hours halved for nearby residents  Physical activity benefits declined with increasing distance from the greenway  Retrofitting an urban greenway can be successful in promoting active lifestyle

Summary A growing body of research links traffic‐related environmental factors to childhood obesity; however, the evidence is still inconclusive. This review aims to fill this important research gap by systematically reviewing existing research on the relationship between traffic‐related environmental factors and childhood obesity. Based on the inclusion criteria, 39 studies are selected with environmental factors of interest, including traffic flow, traffic pollution, traffic noise, and traffic safety. Weight‐related behaviours include active travel/transport, physical activity (PA), and intake of a high trans‐fat diet or stress symptoms; weight‐related outcomes are mainly body mass index (BMI) or BMI z‐scores and overweight/obesity. Of 16 studies of weight‐related behaviours, significant associations are reported in 11 out of 12 studies on traffic flow (two positively and nine negatively associated with PA), five out of six studies on traffic safety (four positively and one negatively associated with PA), one study on traffic pollution (positively with unhealthy food consumption), and one study on traffic noise (negatively associated with PA). Among 23 studies of weight‐related outcomes, significant associations are reported in six out of 14 studies on traffic flow (five positively and one negatively associated with obesity outcome), seven out of 10 studies on traffic pollution (all positively associated with obesity outcome), and two out of five on traffic noise (all positively associated with obesity outcome). Our findings show that long‐term traffic pollution is weakly positively associated with children's BMI growth, and traffic flow, pollution, and noise could affect weight‐related behaviours. Associations between traffic density and noise and weight status are rather inconclusive.