Considering it would increase the cargo capacity of a motorcycle while still retaining a lower fuel consumption than a compact car, could it qualify as an "eco-friendly" vehicle?
Since they also require less raw materials to be made of, and subsequently a smaller amount of them is required to make replacement parts, it also seems like an environmental advantage. EFI is getting widespread even in small motorcycles, and Honda even makes some flexfuel ones able to run on ethanol. Also, the side-car can be eventually considered a good platform for experiences with alternative fuels such as CNG, or even some sort of hybrid conversion.