When you really think about it, just about every vehicle that's on the road is either a car or motor bike. Even trucks, vans and scooters are essentially variations of the two. So dominant are these technologies that they've become the de facto starting point for nearly all efforts to develop a form of personal transportation that's more fuel-efficient and eco-friendly.
But students from the University of Adelaide have shown what's possible when engineers completely disregard the status quo and experiment with some far out designs. Their invention, the Electric Diwheel With Active Rotation Damping or EDWARD, is neither a car or motorcycle. Instead, it functions by borrowing design principles from both.
The vehicle consists of two axially-aligned wheels and a passenger cabin sandwiched in between. It has a top speed of 40 kilometers an hour, an incline of 12 degrees and is controlled using a joystick. Equipped with energy-harnessing regenerative braking technology, it's also so bare bones and lightweight that drivers can expect to squeeze an hour's worth of intense driving from the contraption's onboard sealed lead acid batteries (hint: They're the same batteries found in standard cars). The inventors state that "sensible" use would allow drivers to operate the diwheel for much longer before having to swap out the battery.
Diwheels have been around for a while -- a century and a half at least. But earlier models were either human-powered or relied on an IC engine. They also tended to cause major discomfort for the driver due to an effect known as gerbiling in which stopping the wheels didn't exactly stop the momentum inside the cabin, causing the passenger to take a bit of a tumble. EDWARD eliminated this problem using an inbuilt dynamic lateral stability and slosh control system (a form of active damping) that keeps the cabin stable during sudden braking and acceleration maneuvers.
While nobody should expect Honda or any other major automobile manufacturer to start production on diwheels, what the students have demonstrated is that energy efficiency and cutting CO2 doesn't have to be all about engines or batteries.