Motorcycle

Environmental impact
In 2007 and 2008, motorcycles and scooters, due to good fuel efficiency, attracted interest in the United States from environmentalists and those affected by increased fuel prices. Piaggio Group Americas supported this interest with the launch of a "Vespanomics" website and platform, citing lower per-mile carbon emissions of 0.4 lb/mile (113 g/km) less than the average car, a 65% reduction, and better fuel economy.
Other sources, however, claim that while motorcycles produce much less pollution in terms of greenhouse gases, a motorcycle can in some cases emit 10–20 times the quantity of nitrogen oxides (NOx) when compared to the NOx emissions of a car. This is because many motorcycles lack a catalytic converter to reduce NOx emissions, and while catalytic converters have been used in cars long enough that they are now commonplace, they are a relatively new technology in motorcycles. Many newer motorcycles (such as later models of the Yamaha R1 and Suzuki GSXR1000, as well as most BMWs which have included catalytic converers since the 1990s) now have factory fitted catalytic converters. Along with other technologies that have taken longer to appear in motorcycles (e.g. fuel injection, anti-lock brake systems), catalytic converters are becoming increasingly commonplace.
United States Environmental Protection Agency 2007 certification result reports for all vehicles versus on highway motorcycles (which also includes scooters), the average certified emissions level for 12,327 vehicles tested was 0.734. The average "Nox+Co End-Of-Useful-Life-Emissions" for 3,863 motorcycles tested was 0.8531, for a difference of about 16%, not the claimed 10X factor. Likewise, if one looks at how many of the 2007 motorcycles tested were also catalytic equipped, 54% of them, 2,092, were equipped with a catalytic converter.