This study will focus on parents' decision-making regarding their children's active school transportation, considering the fact that parents are the primary decision makers for their children's school transportation. The study aims to: 1) Examine the effects of parents' perceived physical environment - especially safety perceptions - in the relationship between objective physical environment and active school transportation; 2) Examine the moderating role of parents' and children's personal and social factors in the relationship between objective physical environment and active school transportation; 3) Examine the environmental supports and threats for low-income Hispanic children, considering walkability, safety, and ambient environment, and explore if these children have any specific needs that are different from their affluent white peers; and 4) Identify an acceptable walking distance for elementary school children and test whether this distance varies by race (Hispanic vs. non-Hispanic whites) or physical context (e.g., urban vs. suburban). For each study school in the Austin Independent School District, the findings about its safety, walkability and ambient environmental quality will be summarized as an executive summary. A policy support tool will be developed to help policy makers consider the mediating role of perceptions and the moderating role of population characteristics during their decision-making process. An Active School Transportation Index will also be developed based on the significance of objective physical environmental variables. As a practice-oriented tool, it can guide decision-making regarding locations and scale of new school and boundary changes of existing schools. This product will be introduced to the city, school district, planning department, transportation department, as well as the national Safe Routes to School Program.