Alternative transportation refers to methods of transportation outside of the traditional automobile, usually specifically referring to methods that create fewer emissions. Examples include bicycles and high-occupancy modes of transport like buses, trains and carpools. Hybrid vehicles may also be included in this category, because while they do use some gasoline, their main purpose is to emit fewer greenhouse gases than traditional cars. The production of greenhouse gases, or pollution, contributes to climate change. Environmentalists advocate alternative transportation because it helps to dramatically reduce the amount of greenhouse gases in the atmosphere, and thereby slow climate change. (Photo: Flickr)