This thesis intends to demonstrate how capital infrastructure investments can be targeted objectively, using the "Safe Routes to School" (SRTS) program for context. SRTS impacts physical activity, a determinant of childhood obesity by encouraging children’s regular active transportation use. This thesis supports the widespread implementation of SRTS and has developed the "Shelling Model" to objectively identify schools for programming. Accordingly, the "Shelling Model" aims to objectively identify physical and socio-economic environment variables impacting HISD-E middle school neighborhoods’ walkability. The "Shelling Model" is a first step in creating a walkability index for which pedestrian orientation levels can be identified and schools targeted. This model facilitates the identification of variables, providing insight into neighborhood walkability levels. Revealed by statistically significant variables, in combination with Walkscore and Catchment regression models’ respective 45.5 and 13.6 Adjusted R-Square values, the "Shelling" archetype proves a useful tool for investigating the walkability of HISD-E middle school neighborhoods.