Emission Control and Air Pollution Module

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More Historical Background

The 1990 Clean Air Act - What's New?

The new Clean Air Act strengthens components of the earlier law. The tailpipe standards for cars, buses, and trucks have been tightened, and Inspection and Maintenance (I/M) programs have been expanded to include more areas and allow for more stringent tests.

The 1990 law also introduces several entirely new concepts with regard to reducing motor vehicle-related air pollution. For the first time, fuel is considered along with vehicle technology as a potential source of emission reductions. And more attention is focused on reducing the growth in vehicle travel. The new provisions include:

  • Emphasis on Fuels

The act mandates that improved gasoline formulations be sold in some polluted cities to reduce emissions of carbon monoxide or ozone-forming hydrocarbons. Other programs set low vehicle emission standards to stimulate the introduction of even cleaner cars and fuels.

  • Nonroad Engines

The 1990 Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to consider emissions from off-highway vehicles as well as from highway vehicles such as cars and trucks. The so-called "nonroad" category includes boats, farm equipment, bulldozers, lawn and garden devices, and construction machinery. Because nonroad engines have not been previously regulated for pollution, they can be very dirty. EPA has determined that emissions from nonroad engines are a significant source of urban air pollution and is working with industry and the public to develop effective control strategies.

  • Clean Transportation Alternatives

The law requires the smoggiest cities to limit growth in vehicle travel by encouraging alternatives to solo driving. In areas where ozone levels exceed certain criteria, employers of 100 or more will be asked to find ways to increase the average number of passengers in each vehicle for commutes to work and during work-related driving trips.

What Has Emission Control Meant for Air Quality?

Efforts by government and industry since 1970 have greatly reduced typical vehicle emissions. In those same years, however, the number of miles we drive has more than doubled. The increase in travel has offset much of the emission control progress. The net result is a modest reduction in each automotive pollutant except lead, for which aggregate emissions have dropped by more than 95 percent. With ozone continuing to present a persistent urban air pollution problem, future vehicle emission control programs will emphasize hydrocarbon and nitrogen oxide reductions. Carbon monoxide control will remain critical in many cities, and limits on vehicle-generated carbon dioxide may become important in the future.


The 1990 Amendments: The View from the Driver's Seat

Typical drivers will probably not be aware of many vehicle and fuel changes manufacturers are making in response to the 1990 Clean Air Act, although these changes could add $200 to the cost of a car and a few cents per gallon to the cost of gasoline. But there are other programs that drivers will notice, especially in areas with air pollution problems.

New 1994 and later model cars must be equipped with "onboard diagnostic systems." These systems feature dashboard warning lights that alert drivers to malfunctioning emission control equipment. Controlled by the vehicle's computer, the onboard diagnostic system must also be capable of storing trouble codes that help mechanics pinpoint the malfunction.

Another change involves tampering and misfueling. Such activities have always been discouraged, but were previously illegal only for commercial operations. "Backyard mechanics" now are also subject to stiff penalties for deliberate tampering.

For drivers in polluted cities, more changes will be apparent. Some cities will have to start I/M programs to check vehicle emissions on a regular basis. Areas that already require I/M testing may have to institute more stringent programs.

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