Low-Emission Vehicles

Low-emission vehicles (LEVs) are a subset of the global motorized road transport fleet that produces comparatively fewer emissions than those produced by a conventional internal combustion engine (ICE) fueled by gasoline or diesel.

The reduction in emissions is achieved through the implementation of a range of technological improvements that increase the efficiency of the vehicle or through the utilization of alternative fuels, such as biofuels, gas—most commonly compressed natural gas (CNG) or liquefied natural gas (LNG)—electricity, and hydrogen. Any of these alternatives may also be used in combination with conventional fuels. One example is the current hybrid-motor systems used in passenger automobiles, which use both battery technology and fossil-fuel-powered internal combustion. While the term vehicle could be wide-ranging, most of the policy focused in this area, as well as the technological developments made, have been in the passenger car and light-duty truck sectors.

Early measures to control vehicle emissions, such as the catalytic converter that became standardized in the mid-1970s in the United States, around the time of the introduction of the Corporate Average Fuel Economy (CAFE) regulations. They were subsequently introduced worldwide and have given way to more systemic vehicle improvements designed to reduce both emissions of air pollutants such as carbon monoxide, nitrogen oxides (NOX), volatile organic compounds and atmospheric particulate matter. More recently, LEVs have been introduced to reduce the impact of greenhouse gas emissions, primarily carbon dioxide (CO2).

The issues of pollution addressed by air quality standard legislation and climate change have some complementary solutions, but there are some measures, such as the promotion of diesel engines as a comparatively lower carbon fuel, that actually exacerbate air pollution and the associated health impacts because of the increased levels of NOX emitted by diesel-fuel engines. Such trade-offs emphasize the need to move toward non-fossil-fuel-based technology but also expose the complexity inherent in such shifts.

The term LEV gained prominence after California introduced a LEV program in 1990 that mandated tailpipe emissions standards more stringent than those required by the federal government.

Several variations in terminology have emerged over the past 20 years to differentiate between particular vehicle types. As well as LEVs and zero-emission vehicles (ZEVs), terms that have entered the parlance of the auto manufacturing community include transitional low-emission vehicles (TLEV), super-low-emission vehicle (SLEV), partial zero-emission vehicles (PZEV), ultra-low-emission vehicles (ULEV), super-ultra-low emission vehicles (SULEV), and advance-technology partial-zero-emission vehicles (AT-PZEV). Most of the acronyms developed as California's legal response has progressed, although the utility of such an array of distinctions has been questioned.

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Government and Industry Initiatives

Over the past two decades, government and industry initiatives have been developed across the world to promote the introduction of LEVs, with the United Kingdom government even establishing an Office of Low Emission Vehicles to manage the Department of Transport's work in this area.

An engineer in a thermal cell research facility at the U.S. Department of Energy's Argonne National Laboratory attaches hoses to an automobile to measure tailpipe emissions in 2009.

Following the introduction of the CAFE standards in the United States in the mid-1970s, so-called voluntary agreements to increase the fuel efficiency of new vehicles were struck among members of major auto-manufacturing associations worldwide, including the European Automobile Manufacturers' Association, the Japan Automobile Manufacturers Association, and the Korea Automobile Manufacturers Association in the mid-1990s. The voluntary agreements were largely unsuccessful in delivering the scale of reduction of tailpipe emissions that were targeted by the companies, and in Europe, at least, manufacturers are now mandated to deliver reductions through the 2009 CO2 regulations for cars.

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