A comprehensive research program for the characterization of storm water runoff from an Arizona highway was conducted from January through December 2007. The study area covered a portion of the Loop 202 freeway west of Mesa Drive to a retention basin east of Lindsay Road in Mesa, Arizona. Storm water samples were collected from two storm water detention basins and a discharge point to the Salt River. The study was conducted by manually collecting storm water samples with passive automatic samplers and analyzing them for various roadway constituents. A primary objective of this research effort was to establish baseline values of constituents in ADOT highway runoff, aiding in the evaluation of related best management practices. A total of 16 storm water samples was collected from the research area between January 2007 and December 2007.

Some freeway users complain that new freeway segments fill up with traffic during peak hours immediately after construction. Because of this concern, the debate about the costs and benefits of freeways often centers on relieving congestion. The literature states that the long-term relief of congestion is an elusive goal. While congestion is a pervasive feature of freeways, it does not mean that constructing them is useless. This study helps to demonstrate that the great benefit of freeways is to facilitate travel rather than reduce peak-hour congestion. The study finds that the facilitated travel far outweighs the cost of freeway construction. Even if new freeway capacity becomes congested during peak travel hours, there is still great benefit in the increased travel mobility that can be accommodated.