A pro-highway group has found that California's air is getting better.

According to The Road Information Program, overall emissions of smog-forming pollutants in California decreased 30 percent between 1985 and 1999. The greatest contributor to that decline was a 36 percent decrease in smog-forming emissions from cars, trucks, buses and other highway vehicles.
TRIP examined air quality trends in California using recent data from the U.S. Environmental Protection Agency.
The group credits increased use of lower-emitting vehicles, cleaner fuels and increased vehicle inspection and maintenance as contributors to the reductions in pollutants.
"This isn't just a story of a significant drop in emissions," said Larry Fisher, executive director of Transportation California, a highway advocacy group. "This is a remarkable improvement in light of the state's dramatic growth in population, vehicle miles traveled and economic output."
From 1985 to 1999, California's population increased by 25 percent, vehicle travel increased by 45 percent and the gross state product, adjusted for inflation, increased by 62 percent.
The San Francisco Bay area had the best record with a 39 percent reduction of smog-forming emissions between 1985 and 1999. Smog-forming emissions in the Los Angeles, San Diego and Sacramento regions decreased by 30, 30 and 24 percent, respectively.
Technology promises to deliver more improvements. Diesel emissions, which emit 40 percent of vehicle NOx in the state, are expected to be reduced by 90 percent in California by the year 2010. State and federal law will require the sale of low-sulfur diesel fuel by 2006 and significantly cleaner diesel engines by 2007.
Despite the improvements, seven California metropolitan areas continueto have unhealthy air days and are out of compliance with federal clean air standards: Los Angeles, the southeast desert, Sacramento, Ventura County, San Diego, San Joaquin Valley, and the Santa Barbara-Santa Maria-Lompoc area. Los Angeles is the only California urban area classified "extreme" in its noncompliance. The desert, Sacramento and Ventura areas are classified "severe." San Diego, San Joaquin Valley and the central coast region are classified "serious." The San Francisco Bay area is not on the list.