What is the aerodynamic drag force in pounds due to the box alone at a velocity of 60 mph. Clearly, the Bus has the highest efficiency. We discussed flywheels and their use in hybrid vehicles. Fly wheels can be used in a regenerative braking system where kinetic energy of your automobile is stored in the flywheel when ever you apply the brakes.
Batteries have limited energy on one charge.
The pollutants from fuel cell use are fewer. Batteries contain lead, lead oxide, both with toxic heavy metal, lead. Essentially none of our present automobiles are using fuel cells. Getting hydrogen from water is more expensive than from gasoline at the moment. In other words, hydrogen is not a primary fuel.