They're more fuel efficient than most cars. They consume fewer resources to build and maintain than cars. On the other hand, sustainable transportation advocates view motorcycles as part of the problem. Emission standards for motorcycles came into effect in this year's 1997 models. According to AirCare, most motorcycles made since 1981 meet US emissions standards.
Motorcycles are, for the most part, single occupant vehicles.
Legislation says they must behave in traffic as an automobile does, so they do take up precious space on our roads. And they contribute to the level of noise pollution in our crowded urban centres. Check out links to other motorcycle-related sites and find out more.