Traffic safety has become an important concern in recent years. Built environmental characteristics have been identified as a critical factor in affecting traffic safety. However, several research gaps remain in the understanding of the built environment-traffic safety relationship. This dissertation explored the complex associations between built environmental characteristics and traffic safety on neighborhood and school scales in the city of Austin, TX. In Aim 1-1, the author examined local relationships between built environmental attributes and crashes with different levels of injury severity in census block groups in Austin, TX. The results showed that traffic volume, highways/freeways, arterial roads, and commercial uses had consistently positive impacts on total, fatal, serious, minor, and no injury crashes. Some built environmental factors (e.g., highway/freeway, arterial road, and commercial use) had a stronger effect in some areas but were weaker predictors in other places. In Aim 1-2, this study explored the disparity issue in crashes with different levels of injury severity across neighborhoods with different economic statuses and ethnic compositions in Austin, TX. The findings indicated that some built environmental variables (e.g., arterial road, office land use, and school) only showed significant impacts on traffic safety in areas with high percentages of non-white population and population below the poverty line but not in low-percentage areas. Aim 2 used two-level binomial logistic models to investigate the influence of built environments on crashes involving elementary school-aged children during school travel time in 78 elementary schools in the Austin Independent School District (AISD), TX. The results showed that roads with higher posted speed limits, highways/freeways and arterials, higher percentages of commercial, office, and industrial land uses around street segments significantly increased the probability of crashes. In conclusion, it is necessary to develop tailored policies with regard to the characteristics of each area. Moreover, policies related to arterial roads, office uses, and schools may not equally promote traffic safety in areas with different economic statuses and ethnic compositions. For the school travel safety, planners should design a complementary network of low-speed roads in the vicinity of school areas, and arrange roads with residential uses around school area.
