The impact of an air quality advisory program on voluntary mobile source air pollution reduction

Air pollution from mobile source emissions is a major cause of air quality degradation in the Denver, Colorado, metropolitan area. The projected increase in both population and vehicle miles driven, coupled with the high altitude, predominantly clear skies, and prevalent wintertime temperature inversions aid in the formation and retention of pollutants. The Colorado Department of Public Health issues an air quality advisory daily during the high pollution season (November 1–March 31) with the objective of improving air quality through voluntary driving restrictions and a mandatory wood burning ban. We hypothesized that the advisory had no effect on commuter behavior due to lack of awareness and understanding, lack of alternative means of travel, or lack of concern. We mailed an anonymous, self-administered survey to 1000 commuters living in the cities of Boulder and Westminster, Colorado. Despite the fact that the vast majority of the respondents were aware of the daily advisory (94%), understood what it meant (93%), and heard the posting at least once a day (71%) in time to choose alternative forms of transportation, the advisory did not alter commuter travel. Commuters traveled mainly as the sole occupant of a car and most (76%) never changed the way they commuted based on the daily advisory. Many claimed schedules or work locations did not allow them to use alternative transportation methods. We suggested a practical way to improve the advisory would be to reduce or eliminate public transit fares on poor air quality days.