BACKGROUND AND HISTORY

In 1972, the number of days that exceeded the federal criteria pollutant levels for carbon monoxide had topped out at 125. Due to the growing concern about pollution generated within the city by cars and trucks (mobile sources), serious efforts began to decrease the visible, physical, health, and environmental effects of transportation. One of the first efforts at decreasing vehicular air pollution began in 1979, when city council passed the smoking vehicle ordinance making it against the law to operate a vehicle with visible tailpipe emissions within Denver boundaries.

Throughout the 1980's, stricter federal emission guidelines for vehicles led to several technological advancements in engine design including catalytic converters, fuel injection, and oxygen sensors. Although these advances significantly contributed to reducing the days Denver exceeded the federal standards--by 1990 only three exceedences were reported--Denver was still classified as non-attainment for carbon monoxide by the EPA.

The non-attainment status provided the impetus to pass additional legislation during the 1990's to further reduce mobile source pollution. The idling vehicle ordinance was passed in 1990 prohibiting vehicles within the city limits to idle more than 10 minutes in any one-hour period of time.