Cars and other motor vehicles have been responsible for approximately half of all air pollution in the United States. This pollution is generated from both direct tailpipe emissions and mechanical wear and tear on the different parts of the vehicle. The main emissions of cars include carbon monoxide, hydrocarbons, nitrogen oxides, lead, and particulate matter. The three types of automotive emissions are evaporative emissions, refueling losses, and exhaust emissions.
It is interesting to note that a car does not always need to be running to emit pollutants. Emission test results of individual vehicles are compiled to assess the emission performance of various classes of vehicles, the effectiveness of the test program, and other regulations related to emissions. This process involves testing a representative production vehicle and component parts in an accredited facility. Advances in engine and vehicle technology have continuously reduced the toxicity of exhaust gases leaving the engine, but these alone have generally proven to be insufficient to meet emissions targets.
The increasing import of second-hand vehicles into cities has created high levels of traffic congestion, enormous air pollution, and increased greenhouse gas emissions. Vehicle emission control is the study of reducing emissions produced by motor vehicles, especially internal combustion engines. Some states in the United States are using technology that uses infrared and ultraviolet light to detect emissions as vehicles pass on public roads, thus eliminating the need for owners to go to a test center. Model-specific CO2 limits allow for higher emissions for heavier vehicles; however, the average figures for each manufacturing group must meet the overall objective.
The effect of stricter European standards on vehicle emissions has been to accelerate the introduction of greener vehicle technologies.
