(cm) It isn't only the noise that motorcycles make that is above average; their exhaust emissions also pollute the environment disproportionately. This second result comes from an investigation from Ana-Marja Vasic and Martin Weilenmann from the Swiss Federal Laboratories for Materials Testing and Research (EMPA) in which the researchers compared the emissions of 8 powered two-wheelers with 17 petrol driven passenger cars. The results of their study were published this month in Environmental Science & Technology (1).

For their measurings the scientists simulated the road performance on urban and rural roads as well as highways on their test bench in Dübendorf. Massive differences were ascertained under urban driving conditions with regard to hydrocarbons. If one calculates the exhaust emissions of the estimated Swiss motorcycle fleet, based on the results for the tested motorcycles, these two-wheelers emit 16 times more pollutants than all passenger cars. On country roads the ratio is still almost 4 to 1. As far as carbon monoxide is concerned, the level produced by motorcycles is higher to a factor of 3. The proportion of the carbon dioxide and nitric oxide emission of motorcycles, on the other hand, is lower: the ratios here are 50 and 5, respectively. This contribution is not negligible according to the researchers, especially if one considers that there are far fewer motorcycles than cars on Switzerland's roads.

Even though they admit that the types of motorcycles and cars used in their study might not be representative, they conclude that motorcycles should be subject to new regulations and controls in view of their over proportional tailpipe emissions.