The main reason is the simplicity, which results in a much cheaper vehicle. For instance, the compressed air tanks are lighter and, of course, cheaper than an equivalent lithium-ion battery. The reduced weight results in better gas mileage, and Citroen has added some other tricks to increase efficiency. Those include composite materials and aluminum to further reduce weight, along with air intakes and a rear spoiler. It even has wheel covers that aerodynamically cover the wheel during cruise, but retract to prevent overheating during braking -- one of those "wow, cool" car show features that rarely make it into production.

And mass-producing the vehicle is the point, according to Citroen. It wants to have a hybrid option in its vehicle lineup that costs about the same as diesel engine upgrade -- that is to say, only several thousands of dollars more. That's a steep discount from most hybrid vehicle options -- the Honda Civic hybrid costs up to $8,000 more than the standard model. As for when, and how much, the French car maker was cagey on details, but thinks such a vehicle could arrive to market as early as 2016.