The article discusses the energy efficiency of electric and electric/flywheel hybrid vehicles. The researchers used a digital simulation program and test data to compare the power train efficiency of these vehicles. They found that regenerative braking doesn't significantly improve vehicle range, making its complexity unnecessary. Additionally, electric/flywheel hybrids are not cost-effective due to their complexity and poor performance at constant speeds. Surprisingly, even with coal as the main energy source, electric cars are not energy conservative. Less coal is consumed when it is liquefied for use in internal combustion engine vehicles than when it is burned to generate electricity for electric vehicles, even with advanced batteries.