Despite widespread efforts to increase physical activity, less than half of Americans reach nationally recommended levels . The relationship between neighborhood of residence and physical activity has become an important area of investigation based on initial findings suggesting that neighborhood of residence differentially influences physical activity rates . When aggregated at the neighborhood level, socioeconomic status (SES) [3–6], access to physical activity resources [3, 7], and the quality and accessibility of the pedestrian environment [7–9] appear to influence physical activity, although most investigations to date have typically relied on broadly-defined existing records (e.g., census data, business telephone listings) or self-reports of the presence or absence of neighborhood factors .
Several studies have found that residents in low SES neighborhoods report lower physical activity levels than residents of medium to high SES neighborhoods, even after adjusting for individual differences (e.g., income) [3–6]. This relationship has been hypothesized to reflect fewer physical activity resources and opportunities. In contrast, other studies have found increased walking (related to poverty and renting)  or overall energy expenditures  among those living in lower SES neighborhoods. Lower SES neighborhoods tend to have higher residential density, more renters (than owners), social norms of congregating outdoors, and more opportunities for energy expenditure through work or travel [11, 12]. In addition, individuals in lower SES neighborhoods have lower rates of automobile ownership, increasing their reliance on public transit or non-motorized transportation modes .
Simply having more parks available has been found to facilitate walking and bicycling . Lower-income urban adults with access to walking/jogging trails and parks have reported higher rates of physical activity (OR = 1.89 and 1.95, respectively) than those without trail and park access. As the number of available physical activity resources increased, so did the likelihood of meeting physical activity guidelines . Nevertheless, low SES neighborhoods often have few physical activity resources available [6, 7], and many are low quality or poorly maintained [15, 16].
Neighborhood aesthetics also appear to influence physical activity. For example, the highest rates of resident walking are found in areas that are safe and aesthetically pleasing [8, 9]. At the same time, physical decay, including "incivilities" (e.g., litter, vandalized buildings, graffiti), influences perceptions of neighborhood quality, impacting residents' health behaviors . In neighborhoods with high rates of poverty and low rates of home ownership, the presence of incivilities may create settings that appear unappealing and unsafe, discouraging outdoor physical activity . Brownson and associates found that lower-income individuals reported higher frequencies of incivilities (i.e., heavy traffic, unattended dogs, and air pollution) as barriers to physical activity than higher-income individuals,  demonstrating the complexity of understanding neighborhood influences on physical activity.
Walking, the most popular physical activity reported by Americans , may be especially sensitive to neighborhood conditions. Walking on a regular basis can result in significant health benefits, as moderate intensity physical activities equivalent to brisk walking (i.e., a daily, 30 minute brisk walk) help prevent numerous diseases and early death [5, 6]. Despite the popularity and promising health benefits, few individuals get sufficient amounts of walking to gain health benefits . In addition, the connectivity of streets, or the availability of direct and alternative travel routes between two destinations, fosters higher rates of resident physical activity for transportation, such as walking or bicycling [2, 18]. Streets designed in a grid pattern with few obstacles (e.g., highways or other pedestrian barriers) preventing travel between destinations have high connectivity . Street connectivity has been positively related to the number of minutes of moderate daily physical activity; neighborhood residents with high connectivity were 2.4 times more likely to meet walking recommendations than residents of neighborhoods with lower connectivity .
Previous research has used both self-reported perceptions and objective measurements of the environment to link elements of the built environment to physical activity [see [20–22] for reviews]. More researchers have studied self-reported perceptions of the environment than objective measures of the environment, and most studies on the built environment and physical activity have not directly assessed the environment by relying on pre-existing data sources . Studies using objective and direct measures may be preferable over self-reported measures, because self-reported measures may reflect individual biases. Pre-existing data sources do not provide information about the modifiable characteristics of the environment, and direct objective measures can help identify these built environment elements that may be modified or enhanced via policy interventions [20, 23]. There is a need to identify these modifiable characteristics of the environment that affect physical activity  using instruments that include concrete measures of the physical dimensions of the of the built environment factors under investigation . Despite much interest and preliminary findings, many questions remain concerning the nature and scope of the relationship between the built environment and physical activity .
This study was designed to investigate how measured environmental factors (i.e., street connectivity and the number, type, accessibility, and quality of physical activity resources) are related to self-reported walking and vigorous physical activity for residents of low-income public housing developments. We hypothesized that residence in neighborhoods with higher street connectivity would be associated with more days walked per week and a greater likelihood of meeting guidelines for moderate physical activity. Further, we hypothesized that residence in neighborhoods with more physical activity resources and fewer incivilities would be associated with more days of vigorous physical activity.