Background:
Obesity is a critical public health issue affecting all children in the United States. Children in low-income and ethnic minority populations have a particularly high risk for being overweight and have low rates of physical activity. Increasing rates of active transport to school offers a means of increasing physical activity levels among youth. Most research on walking and biking to school has focused on the influence of built environment and individual demographic characteristics. These studies have shown that distance has the strongest effect on the likelihood of walking and biking, but other factors including urban form, perceived environment and individual demographic characteristics also affect behavior.

Objectives:
Lacking from much of the existing literature is an understanding of how the social environment affects children’s school travel - particularly in areas where the built environment supports walking. This study fills this gap in knowledge by assessing how dimensions of the social environment identified in previous research - child-centered social control, intergenerational closure, social cohesion, and safety from crime - correlate with walking and biking to school after controlling for trip distance and individual demographic factors.

Methods:
This analysis uses data from a cross-sectional survey of parents of 10 to 14 year olds living in highly walkable neighborhoods in or near Oakland, California. Respondents were drawn from the Kaiser Permanente Northern California member base and 432 interviews were conducted between August 2006 and May 2007, of which 425 were useable. The raw response rate was 26% and 34% after adjusting for ineligible households. The cooperation rate among reachable households was 58%. Measures of the social environment were adapted from previous studies and are based on parental responses to Likert scale questions. For each of the 4 scales - child-centered social control, intergenerational closure, social cohesion, and safety from crime - the average response was computed and standardized. The average treatment effect of having a higher (top 2 quintiles) score versus lower (bottom 2 quintiles) was estimated by comparing rates of walking and biking between the 2 groups using nearest neighbor matching across control variables such as child’s age, child’s race, and distance to school. The nnmatch function in Stata (College Station Texas, version 9.2) was used to conduct the analysis assuming heteroscedastic errors.

Results:
Parental reports of living in areas with higher levels of child-centered social control (Average Treatment Effect (ATE)=0.13, p<0.01) and social cohesion (ATE=0.21, p<0.01) were positively associated with increased rates of walking and biking to school. Living in areas with higher levels of intergenerational closure (ATE=0.03, p=0.60) or a safer perceived environment (ATE=0.10, p=0.18) had no significant association with walking and biking to school. These treatment effects were observed after nearest-neighbor matching on child’s age, number of household vehicles per household adult, income, and exact matching on race/ethnicity (Non-Hispanic White, Hispanic, Other), and distance to school (0-0.5 miles, 0.5-0.75 miles, 0.75-1.5 miles, >1.5 miles). Results were robust to model specification with binary logit models of the decision to walk or bike to school showing a significant and positive coefficient on the binary indicator of living in a high social cohesion or child-centered social control neighborhood.

Conclusions:
This study provides evidence that parents are significantly more likely to allow their children to walk and bike to school when they believe other adults in the area will watch out for their children and they know and trust their neighbors. The results suggest that Safe Routes to School (SRTS) programs need to do much more than improve safety near schools through infrastructure improvements. Improving the physical environment for walking is a necessary but not sufficient condition for increasing walking and biking to schools. To be more effective, SRTS programs need to address parental concerns about neighborhood social cohesion. This can be achieved by outreach efforts that provide parents ways to interact informally and by instituting programs such as walking school buses which provide adult escorts for children on their way to school.\

Support:
This research was supported by the Active Living Research Program of the Robert Wood Johnson Foundation (Round 3).