Hybrid bicycles are old news. As we know them, they combine two forms of power: human-generated, in the form of pedaling, and a second, non-human energy-generator, either electric or gas.

Gas-hybrid bicycles came first, and were simply traditional bikes modified with an add-on kit [source: NYCeW]. Cyclists have long been able to buy wee internal-combustion engines to soup-up their two-wheelers, essentially creating gas-powered motorcycles with working pedals. Not the safest way to travel, perhaps, but a noteworthy upgrade. The engine can be turned off and on to accommodate different power needs, and the whole setup is illegal throughout much of the United States [source: NYCeW]. The modified gas-bike is a difficult vehicle to classify when it comes to traffic laws.

The more modern, more common, more expensive and quite legal hybrid bicycle is the human-electric variety. These have been around for years and were once a significant development in green transport, particularly in places like the U.S. where nearly half of all car rides stay within a 2-mile (3.2-kilometer) radius of home [source: USDOT]. These types of bikes come in two basic forms: There's the kind with an electric motor than senses the need for extra power automatically, turning itself on when, say, the rider starts up a hill and then shutting off for the ride down; and the kind with an electric motor the rider manually turns on and off as needed.

The Hybrid Sports Bike, or at least the most recent prototype as of March 2013, uses a manual type of electric-hybrid system. What makes the HSB such an interesting machine is that it adds gasoline to the hybrid equation. Dirty, expensive, non-renewable gas.

And yet, the HSB could end up being a significant leap forward in eco-friendlier travel -- in part because the pedals are somewhat ancillary. The HSB is less a hybrid bicycle than a hybrid motorcycle, according to Bubilek, intended for trips well beyond a few miles from home.

There are other hybrid motorcycle designs, most prototypes as well, using two forms of power, either human and electric or gas and electric [source: Ury]. It's the mere option of using solely human power (along with some design choices affecting maneuverability) that helps distinguish the HSB from what's already out there.