Motorbikes spew out more pollutants than expected

Jan 27, 2006 | MARTINA PETER
Motorcycles in Switzerland are responsible for emitting significantly more pollution than all the petrol-engined cars in the country combined. This is the conclusion drawn by Empa scientists Ana-Marija Vasic and Martin Weilenmann in a study in which they compared the exhaust emissions of eight different motorbikes with those of 17 cars. Both two stroke and four stroke motorcycles performed worse in this respect than the cars investigated, according to their paper which has just been published in the renowned scientific journal «Environmental Science & Technology».
Particularly serious was the difference in emissions of hydrocarbons, above all during the urban test cycle when the quite small Swiss motorbike fleet spews out up to sixteen times more of these pollutants than all the cars registered in the country! During the rural cycle this difference drops to a mere four times. In addition to the carcinogenic effects of certain hydrocarbons, some also exhibit great potential for ozone creation. The two wheelers also emit about three times more carbon dioxide than cars. These results were obtained by the researchers through measurements of the exhaust gas emissions while simulating various driving styles in the Motor Laboratory of the Empa in Duebendorf.
Although in this country as elsewhere the number of cars on the roads far exceeds that of motorcycles, Vasic and Weilenmann have come to the conclusion that exhaust emissions from the latter vehicles are in no way «negligible» and that, from the standpoint of air pollution reduction, action is necessary. The problem is that although since the beginning of 2006 more stringent limits have been introduced for motorcycle exhaust emissions, these limits are still comparatively lax in pollution reduction terms. Furthermore, motorcycles are still not obliged to undergo periodic exhaust testing.

Further information:

Dr. Martin Weilenmann,. Internal Combustion Engines Lab, +41 44 823 46 79,


more information:
Vasic, A.-M.; Weilenmann, M.: "Comparison of Real-World Emissions from Two-Wheelers and Passenger Cars". Environ. Sci. Technol.; 2006; 40(1); 149-154.