5. Key Findings by the U.S. EPA
The EPA indicated that on-road motorcycles are significant contributors to mobile source air pollution and produce more harmful emissions per mile than a car or even a large SUV. In the U.S., the EPA estimated that motorcycles currently account for 0.6 percent of mobile source hydrocarbon (HC) emissions, 0.1 percent of mobile source oxides of nitrogen (NOx) emissions, and less than 0.1 percent of mobile source particulate matter (PM) emissions. Given the more stringent emission standards that have been put in place for other classes of on-road vehicles, the EPA estimated that without tighter regulations for motorcycles, the contribution of on-road motorcycles would increase to 2.2 percent of mobile source HC and 0.3 percent of mobile source NOx by 2020.
The EPA estimates that the more stringent emission standards will have a significant effect on reducing emissions from the fleet of on-road motorcycles, as the cleaner motorcycles enter the market and account for an increasing portion of the in-use fleet. In the year 2020, smog-forming emissions from the on-road motorcycle fleet were forecast to be reduced by 50% for NOx and 61% for HC (includes hydrocarbon exhaust and permeation emissions) as a result of the tighter emission standards.
The EPA noted that the emission reduction associated with adoption of the tighter standards will help reduce the public's exposure to these emissions and help avoid a range of adverse health effects associated with ambient ozone and particulate matter (PM) levels, especially in terms of respiratory impairment and related illnesses. The new standards were also expected to help reduce acute exposure to air toxics and PM for persons who operate or who work with or are otherwise active in close proximity to these sources. Finally, the action will help address other environmental problems associated with these sources, such as reduced visibility in national parks and other wilderness areas.
The EPA concluded that the emission standards described in its final rule are technologically feasible and provided detailed information to support this position in its rulemaking documents. The following is a brief summary outlining the elements supporting the conclusions.
5.2.1 "Class IA" Motorcycles
In the case of Class IA motorcycles (less than 50 cc), the EPA believes that the standards can be met by replacing traditional 2-stroke engines with 4-stroke or possibly with advanced technology 2-stroke engines, and in some cases with catalysts. Progressive regulations in other parts of the world where these types of vehicles are more popular (i.e., Europe, India, Taiwan) are resulting in a transition to 2-stroke direct injection and 4-stroke electronic fuel injection technologies. It is believed that manufacturers will produce emission-controlled motorcycles with engine displacements of less than 50 cc for other markets in advance of the 2006 model year and that complying vehicles will be available for import to the U.S. from these other markets.
5.2.2 "Class IB" and "Class II" Motorcycles
The new emission standards adopted for Class IB and Class II motorcycles are deemed to be technologically feasible as the limits are equivalent to those that have been in place in California since 1982. Further, the vast majority of motorcycles in these classes that are sold in the U.S. (i.e., nationwide) are already certified to these standards: all 24 of the 2002 model year engine families and 22 of 29 2003 model year engine families met these standards. EPA data indicates that of the 29 engine families certified in the 2003 model year, all are powered by four-stroke engines, with a variety of emission controls applied, including basic engine modifications on almost all engine families, secondary air injection on three engine families, and catalysts on four engine families.
5.2.3 "Class III" Motorcycles
The EPA anticipates that the Tier 1 standards for Class III motorcycles (2006-2009) can be met with available control technologies, primarily involving engine modifications rather than with catalytic converters. While manufacturers can use various means to meet the standards, four basic types of existing emission control systems are available to manufacturers that are non-catalyst-based. These include the use of secondary pulse-air injection; the use of systems offering more precise fuel control; better fuel atomization and delivery (e.g., replacement of carburetors with fuel injection systems); and reduced engine-out emission levels resulting from engine modifications. These types of systems are already being used on many recent model year motorcycles. For the most part, it is not expected that manufacturers will need to use advanced technologies such as close-coupled, closed-loop three-way catalyst systems to meet the Tier 1 standards.
The EPA also believes that compliance with the Tier 2 standards (2010 and later) is technologically feasible, although it is recognized that there will be technical challenges for motorcycle manufacturers. In order to the meet the Tier 2 standards, it is expected that manufacturers will use computer-controlled secondary pulse-air injection and some motorcycles will probably also need to use catalytic converters. Manufacturers could also use heated oxygen sensors to measure the amount of oxygen in the exhaust stream and provide feedback to the electronic control module. This approach enables the fuel control system to maintain a tight band around the stoichiometric air/fuel ratio and minimizes the exhaust variability which is experienced by catalytic converters. EPA indicated that several manufacturers are already using closed-loop, three-way catalysts on a number of their products lines and at least one manufacturer has already certified several models to the Tier 2 standards.
EPA indicated its intent to participate in a review planned by California in 2006 to evaluate the progress towards meeting the Tier 2 standards and to determine whether any changes may be warranted to the emission requirements. This review may also include a re-evaluation of whether the Tier 2 standards should be applied to small volume manufacturers.
5.2.4 Evaporative Emission Control
The permeation standards are based on the effective application of low permeable materials or surface treatments standards and are believed to reasonably reflect what manufacturers can achieve through the application of available technology.
5.2.5 Incremental Cost of Emission Controls
The incremental cost to comply with the more stringent emission standards will vary between individual models of motorcycles and will depend on the type of control technologies used, the manufacturing processes, the size of the manufacturer, and other factors. The EPA estimates that increased costs will average approximately $30 per motorcycle for the 2006-2009 model year standards, with an additional incremental cost of $45 for the 2010 model year standards.
The EPA indicated that the technology changes associated with complying with the new emission standards are not expected to adversely affect vehicle performance. In fact, it is expected that some of these technologies (e.g., advanced fuel injection) would improve the performance, fuel economy and reliability of motorcycles.
The EPA also conducted a comprehensive assessment of the potential risks of using catalytic converters on motorcycles in response to previously expressed concerns that motorcycle riders are inherently closer to the engine and exhaust pipes than the drivers of enclosed vehicles. The EPA concluded that catalytic converters can be safely integrated into motorcycle designs.
In support of the above, the EPA indicated that "more than a dozen manufacturers from Indian to Honda and Harley-Davidson have unequivocally stated in the public record-- directly or through their industry association--that motorcycles produced under the new standards will be as safe and have the same or better performance as motorcycles today."
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