The following pollutants are of primary concern to Transportation Planning:
Carbon Monoxide (CO): A colorless, odorless, tasteless gas formed in large part by incomplete combustion of fuel. Human activities (i.e., transportation or industrial processes) are largely the source for Carbon Monoxide production.
Nitrogen Oxides (NOx): A byproduct of fossil fuel combustion, which when combined with Volatile Organic Compounds and heat from sunlight, produces ozone.
Ozone (O3): A colorless gas with a sweet odor. Ozone is not a direct emission from transportation sources. It is a secondary pollutant formed when VOCs and NOx combine in the presence of sunlight. Ozone is associated with smog or haze conditions. Although the ozone in the upper atmosphere protects us from harmful ultraviolet rays, ground-level ozone produces an unhealthy environment in which to live.
Volatile Organic Compounds (VOCs): A byproduct of fossil fuel combustion, which, when combined with Nitrogen Oxides and exposed to heat from sunlight, produces ozone.