A Basic Guide to NOx, VOC, and Ozone Like most air-quality issues, however, the chemical relationship between NOx, VOC, and ozone is complicated. Depending on the proportions of NOx and VOC in the atmosphere, reductions in NOx may increase, decrease, or have no effect on an area's ozone level. Also, while there may be no effect in the area where NOx is generated, NOx may be transported long distances to adversely affect other areas. The answer depends on the specific ITS strategies planned for a particular area. The ITS strategies that accommodate increased travel and support higher speeds are problematic because the models will predict higher NOx emission levels.
Nonconformity is already a real problem for dozens of metropolitan areas.
Some of these areas have developed transportation programs, which may include ITS strategies, that are forecast to improve speed, accommodate more travel, and reduce VOCs. However, they also show NOx increases, often by very small amounts. These strategies tend to decrease emissions. There are complications, however. Ironically, it is possible that NOx will increase as a result of reducing SOV trips.