Phoenix has over 1,400 miles of freeway running through it, with several hundred thousand people living near them.

That is a health hazard. We have taken at least one step to reduce the hazard - built tall sound mitigation walls [which trap some of the fine particulates] but then increased the hazard by laying rubberized roadway.

"...traffic pollution causes asthma attacks in children, and may cause a wide range of other effects including: the onset of childhood asthma, impaired lung function, premature death and death from cardiovascular diseases, and cardiovascular morbidity. The area most affected, they concluded, was roughly 0.2 mile to 0.3 mile (300 to 500 meters) from the highway." {from State of the Air 2012, published by the American Lung Association)

What can we do about this? It affects the future of our city in profound ways.