Air Quality

Improve the region's air quality by reducing the number of single occupant vehicles. Promote alternative travel modes and encourage other measures which will limit emissions from mobile sources.

Policy Background
Air quality is fundamental to the health of people, the environment and the economy. Air quality is strongly affected by production, transportation and population patterns and practices. Poor air quality diminishes the attractiveness of the region as a place to work and live.

Through the Clean Air Act of 1970, as amended 1990, administered by the U.S. Environmental Protection Agency, the Delaware Valley has been classified as a severe ozone non-attainment area. Attainment of the federal ozone standards is required to be met by the year 2005. The complete ozone non-attainment area for the Philadelphia region encompasses the nine county DVRPC region, as well as Salem and Cumberland Counties, New Jersey; New Castle and Kent Counties, Delaware; and Cecil County, Maryland.

Measurement
This indicator, which gauges the effectiveness of air quality regulations from all sources, measures the number of times the Philadelphia non-attainment area exceeded the federal ozone standard for a particular year. Data is collected at ozone monitoring stations in Pennsylvania, New Jersey, Delaware, Maryland and the city of Philadelphia, and will be compared over time.

Results
While this measure can be strongly affected by public policy, it is also influenced by annual weather conditions in the summer season. In order to reach attainment status, the Philadelphia non-attainment area can record no more than three exceedances within a three-year period. After this is accomplished, the EPA can be petitioned to redesignate the region to attainment. During the most recent three-year period of 1997-1999, the region had 11, 7 and 11 exceedances, respectively. While this is an improvement over the 1994-1996 period, which saw 12,47, 9 exceedances, respectively, the region remains far from achieving compliance.

Policy Background
This indicator measures the extent to which commuting alternatives are being used throughout the region. The increasing number of people who drive alone exacerbates motor vehicle exhaust, which is a primary catalyst for ozone. These single occupant vehicle (SOV) trips contribute significantly to the degradation of regional air quality. Alternatives to SOV trips include carpools, vanpools, public transit and biking or walking.

Measurement
The number of resident worker SOV home-to-work trips are provided by the U.S. Department of Commerce's Bureau of the Census every ten years. Resident worker data refers to where workers live as opposed to their places of employment. A lower percentage of SOV indicates a greater usage of transportation alternatives and generally correlates with improved air quality. Data analysis based upon Census information is calculated by DVRPC and is compared over time.

Results
The percentage of SOV trips increased in every county within the Delaware Valley between 1980 and 1990. The region saw the percentage of these trips increase from 59.4% in 1980 to 68.0% in 1990. Bucks and Philadelphia counties occupied the endpoints of the range in 1990, with 80.6% and 44.7% of resident worker SOV trips respectively in 1990. These findings have serious implications for the region's highway congestion levels and air quality.