Generally most people know that motorcycles are highly fuel efficient.

These vehicles can easily get upwards of 2 times the gas mileage compared to a car, truck, or SUV. They are small and lightweight with a majority of their load being the motor and rider. Motorcycles and scooters offer an alternative to high fuel prices but they also have a very dark secret.

In California alone, they accumulate 1% of vehicular miles traveled, but account for 10% of the smog forming emissions which pollute the skies. Unlike passenger vehicles, which have devices to reduce pollutants, motorcycles are not as adequately equipped. Since these vehicles are minimum weight and not enclosed, catalytic converters tend to be less effective in this situation. They are simply too big, too heavy, or too hot to be used in the same manner as passenger vehicles.

These problems coupled with other factors, allows the EPA to impose less strict regulations on bikes. They are allowed to emit more than cars and even tested at lower speeds. The moral of the story is that motorcycles, even small ones, are surprisingly more polluting than Hummers. While you may be conservative in one aspect, you're actually far worse in another.

Source: LA Times