In the first study, we investigate how reducing transportation emissions and other anthropogenic emissions of NOx affects local and national public health in two heavily populated and polluted areas: Los Angeles, CA and New York City, NY. We estimate the Tipping Point (TP) as well as the Break-Even Point (BEP) and show that compounding benefits of NOx control will compensate disbenefits occurred with abatement. In addition, we examine the impact of nationalized vs. localized emission control policies. Next, we focus on the transportation sector and examine the distribution in exhaust emissions on an age-segregated basis for both Canada and the United States. Through the combination of these emission factors with the per-ton public health impacts of NOx and PM from a previous study, we estimate the benefits of (1) reducing the vehicle-miles travelled in terms of $/mile, and (2) removing one average vehicle from the road in terms of $/vehicle-year.