| Vehicle Emissions and the Air Pollution Score What are EPA's emission standards and why are they important? How are vehicles tested for emissions? What do the Air Pollution Scores mean? Why do some apparently identical vehicles have different Air Pollution Scores? What is EPA doing to control pollution from vehicles? The Air Pollution Score helps me compare my vehicle to others, but what are the actual emission standards for my vehicle? Why do we need scores at all? Don't all vehicles meet the requirements? Vehicle Emissions and the Air Pollution Scores What are EPA's emission standards and why are they important? Cars, trucks and other mobile sources account for almost a third of the total air pollution in the United States. EPA's vehicle emission standards for cars and trucks have been in place since the early 1970's. Since that time, vehicle emissions standards have been made increasingly stringent to address this national air quality problem. View the summary of current and historical emission standards. (6 pp, 54k, About PDF) EPA's newest standards, called "Tier 2," provide auto manufacturers with an array of emissions standards they can choose for any particular vehicle model, as long as all the new vehicles they sell in a given model year fall below a required average (bin 5). The emission standards are in effect from the time the vehicle is produced until the vehicle reaches the legally-defined end of its useful life (10 years or 120,000 miles for most cars) - manufacturers are responsible for designing vehicles that will pollute no more than the emission standard limits. More information about EPA's Tier 2 standards can be found here. Due to its unique air quality problems, California has separate emission standards for cars and trucks. Manufacturers wishing to sell vehicles in California must certify that they comply with the California standards. Other states are permitted to adopt California emission standards as well. For the 2008 model year, the following states have adopted the California LEV 2 emission standards: NY, ME, MA, PA, RI, CT, VT. Also, states which border those states may also sell California-certified vehicles. Information about California's emission standards program can be found at www.arb.ca.gov/msprog/msprog.htm. How are vehicles tested for emissions? Before a vehicle manufacturer can offer a new vehicle for sale, EPA requires that various laboratory emission tests be conducted on a vehicle representative of the vehicles that will be sold to car buyers to ensure that the vehicles will meet the emission standards. The tests are designed to simulate a wide variety of actual on-road operating conditions (such as highway driving and city driving). The data from these tests are also used to calculate city and highway fuel economy (mpg) values which appear on the window stickers of new vehicles. More information about vehicle testing can be found here. What do the Air Pollution Scores mean? Each score reflects one set of emissions standards for four different air pollutants: oxides of nitrogen (NOx), carbon monoxide (CO), volatile organic compounds (VOC), and particulate matter (PM). The manufacturer is liable for ensuring that a properly maintained vehicle will emit no more than the given limit of each of these pollutants for each mile that the vehicle is driven. The Air Pollution Score which is a surrogate for the actual emission standards, is on a scale of 0-10, with 10 being the cleanest or best score. Why do some apparently identical vehicles have different Air Pollution Scores? A number of vehicles have different Air Pollution Scores even though they are, by all outward appearances, identical. This is usually due to the fact that there are separate EPA and California emission standards. Manufacturers wishing to sell vehicles in California as well as the rest of the U.S. must separately certify them to comply with EPA and California standards. California standards are generally more stringent than EPA standards due to the unique air quality problems in that state, so this can result in a higher Air Pollution Score for the California version. This does not necessarily mean that the vehicle sold in the rest of the U.S. is "dirtier." In general, if the Underhood Label ID is the same, the vehicle design will be the same as well, meaning that the vehicle has been designed to comply with both sets of standards, so that in reality, the emissions will be at the level of the more stringent of the two standards (California or EPA). What is EPA doing to control pollution from vehicles? EPA has a number of programs underway to ensure that vehicles operate cleanly from the time they are produced until the legally defined end of their useful life (10 years or 120,000 miles for most cars). Information about these and many other programs can be found in the Office of Transportation and Air Quality web site at www.epa.gov/otaq. A few of these are: New vehicle certification program: This program ensures that vehicles are designed to meet the emission standards set by Congress and EPA. For more information see http://www.epa.gov/otaq/cert.htm. On-board diagnostics (OBD): OBD is a computer-controlled system which alerts a driver via a dashboard light that there is a potential problem with the emissions control system of his or her vehicle. OBD is required on all 1994 and newer passenger cars and trucks. OBD systems were also required on trucks up to 14,000 pounds beginning in 2005. More information about these OBD requirements can be found at http://www.epa.gov/obd/regtech/light.htm. EPA has also proposed OBD requirements for heavy-duty trucks over 14,000 pounds beginning in the 2010 model year. More information on heavy-duty OBD can be found at http://www.epa.gov/obd/regtech/heavy.htm Inspection and maintenance: Many cities and metropolitan areas have established inspection and maintenance (I/M) programs that require owners to have their vehicle emissions checked periodically. For more information about I/M programs see www.epa.gov/otaq/im.htm. Emission recall: EPA monitors the emission performance of vehicles on the road to assure that they continue to comply with the emission standards. Vehicle manufacturers are required to build their vehicles to meet emission standards for the useful life of the vehicle. Under the Clean Air Act, if EPA determines that a substantial number of vehicles in a category or class do not meet the stadards in use even though they are properly maintained EPA can require the manufacturer to recall and fix the affected vehicles. View EPA's emission recall activities at www.epa.gov/otaq/recall.htm Emission warranty federally required emission control warranties protect you, the vehicle owner, from the cost of repairs for certain emission related failures that result from manufacturer defects in materials and workmanship or that cause your vehicle to exceed federal emission standards. There are two types of emission warranties: a defect warranty and a performance warranty. The defect warranty covers the repair of emission-related parts that become defective during normal vehicle operation. The performance warranty covers repairs that are necessary because the vehicle failed an EPA-approved I/M inspection. Check your owner's manual for more details about your emission warranties or see http://www.epa.gov/obd/warranties.htm. The Air Pollution Scores help me compare my vehicle to others, but what are the actual emission standards for my vehicle? The emission standards are numerical limits of the various regulated pollutants. A detailed table of emission standards effective for current and past model year cars and light trucks can be found in this Guide. (6 pp, 54k, About PDF) Why do we need scores at all? Don't all vehicles meet the requirements? All vehicles sold in the US must comply with federal emission standards. However, the standards are packaged in various “bins” that manufacturers can choose from, meaning that in a given model year, some vehicles will be cleaner than others. (See the detailed table of emission standards for more information.) (6 pp, 54k, About PDF) By means of the Air Pollution Score the Green Vehicle Guide shows you which vehicles are the cleanest. |