The incomplete combustion of fuel results in the emission of pollutants that are directly harmful to human health. Volatile hydrocarbons released from mobile and other sources, as well as natural sources, combine with nitrous oxides from mobile and other human sources to form regional ozone or smog, a brown haze that interferes with breathing, especially among those who have asthma or other respiratory problems. This chemical reaction occurs in the presence of heat and sunlight and is therefore a problem in the Boston area only in the summer months.
Massachusetts voluntarily adopted California’s stricter automobile fleet emission standards, requiring that 10% of all vehicles for sale in Massachusetts have zero emission by 2004. The Commonwealth also instituted more stringent standards of testing and compliance for all private passenger motor vehicles.
Most buses, trucks, and construction vehicles use diesel fuel. Diesel produces particulates and nitrogen oxides. The latter are precursors to both particulate matter and regional ozone.
How are we doing?
The fleet of new vehicles sold in Massachusetts is becoming dramatically cleaner due to the implementation of tighter emissions regulations under the California program. Already, in the 2003 model year, 55% of the vehicles sold met the Low Emission Vehicle (LEV) standard and 41% met the Ultra Low Emission Vehicle standard. Vehicles meeting even tighter standards are also appearing on the market. The Super Ultra Low Emission Vehicle (SULEV) standard permits significantly less emission than ULEV. In addition, some vehicles meeting the SULEV tailpipe standards are equipped with improved fuel systems designed to eliminate evaporative emissions that would otherwise occur even when the vehicle is not in use. These vehicles are officially designated as Partial Zero Emission Vehicles (PZEV). The 2004 fleet was significantly cleaner than the 2003 fleet, and further improvements are expected as the tighter standards are phased in through the 2010 model year.
The heavy-duty vehicle fleet is also getting cleaner, as more of the in-use fleet meets the tighter emissions standards of 1994 and later model year vehicles. Yet cleaner diesel engines are mandated for 2006, enabled by the required introduction of ultra-low sulfur diesel fuel. The MBTA placed into service 358 new clean-fuel buses in 2003-2004, and another 175 are scheduled to be deployed in 2005. All older MBTA buses have been retrofitted with emissions controls. By 2005, the entire MBTA bus fleet will be low-emission. The MBTA also has begun routine bus emission testing. |
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Click image to enlarge chart "Motor Vehicle Sales by Emissions Controls, Massachusetts: 1996-2003"
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