Driving down fuel usage

Despite their potential to reduce carbon dioxide (CO2) emissions and fuel consumption, electric and hybrid cars and trucks struggled for years to find a solid customer base. Much of the reason came down to cost and convenience: Electric car batteries are expensive, and charging them requires plug-in infrastructure that's still sparse in the United States. Now MIT spinout XL Hybrids is upfitting (and retrofitting) gas and diesel commercial vans and trucks with fuel-saving "add-on" electric powert...