alternative fuels
type: Concept
broader: fuel
definition: The idea of mechanical vehicles for roads once dominated by horses is an old one. It dates back to at least the 15th century, when famed artist Leonardo da Vinci made sketches of self-propelled wagons. [Source: Encyclopedia of Transportation: Social Science and Policy; Alternative Fuels]

concepts
type: Collection
type: ConceptGroup
member: alternative fuels

fuel
type: Concept
narrower: alternative fuels