n F he Robert Wood Johnson Foundation’s Active Living Research Program focuses on the prevention of childhood obesity in low-income and highisk racial/ethnic communities by supporting research to xamine how environments and policies influence active iving for children and their families. This agenda has dvanced transdisciplinary research among researchers rom exercise science, public health, transportation, uran planning, architecture, recreation and leisure, landcape architecture, geography, economics, policy studies, nd education to inform environmental and policy hanges that promote active living among Americans. The papers in this special issue of the American ournal of Preventive Medicine focus on numerous olicy and environmental barriers faced by populations ith low rates of physical activity. Many of these barriers o active living are reflected in broader social and nvironmental justice issues that amplify the context or active living research. One cross-cutting theme throughout the issue is safety oncerns related to crime. Certainly, the more attractive nd safe an environment is perceived, the more likely it ill attract users. However, safety concerns pose a signifcant barrier to physical activity. Safety-related barriers to hysical activity are particularly challenging in distressed eighborhoods where residents, most often low-income eople of color, often limit their time in public spaces to educe their risk of experiencing violent crime. The premise that a well maintained, adequately superised and effectively administered public space is an active living” asset may be relevant only in communities here the physical infrastructure exists and has the ongong support of policymakers, professional administrators, nd citizen stewards. The lack of availability of facilities hat enable and promote physical activity may, in part, nderpin the lower levels of activity observed among opulations with low socioeconomic status and minority ackgrounds. It has been shown that young people in igh poverty communities have fewer community resources, uch as parks and after-school activities, poorer quality chools, and higher levels of environmental hazards. For most of the 20th century, research, policies, and rograms, particularly those that addressed poverty,