What is being done about the smoke coming out of the trucks and buses? Why don these vehicles have to be tested for emissions like cars?
The smoke you are seeing is particulate matter (PM). The smoke is coming from buses and trucks manufactured prior to 1993. Bus and heavy duty truck engines manufactured since 1993 have very tight particulate emissions standards and therefore do not emit visible smoke. It is very common for engines on pre-1993 buses to be rebuilt or replaced which means that these buses have longer lifetime expectancies and are not replaced by newer, cleaner buses. In 1993, EPA adopted a rule (called the Retrofit/Rebuild Program) which requires that when the engines are rebuilt or retrofitted that they must conform to tighter PM emission standards. The retrofit/rebuild program is intended to reduce the ambient levels of PM in urban areas and is limited to 1993 and earlier model year (MY) urban buses operating in metropolitan areas with 1980 populations of 750,000 or more, whose engines are rebuilt or replaced after January 1, 1995.
The smoke you are seeing is particulate matter (PM). The smoke is coming from buses and trucks manufactured prior to 1993. Bus and heavy duty truck engines manufactured since 1993 have very tight particulate emissions standards and therefore do not emit visible smoke. It is very common for engines on pre-1993 buses to be rebuilt or replaced which means that these buses have longer lifetime expectancies and are not replaced by newer, cleaner buses. In 1993, EPA adopted a rule (called the Retrofit/Rebuild Program) which requires that when the engines are rebuilt or retrofitted that they must conform to tighter PM emission standards. The retrofit/rebuild program is intended to reduce the ambient levels of PM in urban areas and is limited to 1993 and earlier model year (MY) urban buses operating in metropolitan areas with 1980 populations of 750,000 or more, whose engines are rebuilt or replaced after January 1, 1995. The emission testing program (also known as the I/M program) tests gasol
