Petition Abolish Road Fund Tax for Motorcycles.

I will start with a question, how is it that certain cars pay zero road tax and much lighter and less fuel hungry motorcycles still have to pay?
Most cars are much heavier than a motorcycle and therefore have a greater detrimental impact on not only the environment but also on our roads.
"Normal" motorcycles have a smaller footprint and use less of the road so why do we pay tax when an exempt car with it's larger size and greater weight does not.
We need to encourage more people to use environmentally friendly transport, abolishing road tax for Motorcycles would be an excellent way to start.
Just look around you there are a great amount of cars being driven around with just one occupant, thats probably around a ton of steel and iron @ 35mpg just to shift one 10st person....we need to get people out of their metal boxes and get them using more economical transport.
Look at most buses; half empty (or less) weighing 10 tons and trundling around the city @ 20mpg.