Energy consumption is the handmaiden of weight. All else being equal, vehicle weight determines the amount of energy expended in driving from point A to point B. The lighter the vehicle is, the less energy it consumes: higher speed and greater range are secondary benefits of lightweighting planes, trains and automobiles. Trucks, buses, bicycles and even scooters benefit from lightweighting. Demand for electric vehicles, more-efficient engines and less pollution is structurally changing the transport industry. Weight savings gained from substituting lightweight materials for heavier ones can be considerable. But, when alternative materials are being evaluated, it is important ...