The Flybus flywheel system (on the right) is attached to the bus's transmission
Gas/electric hybrid vehicles tend to be pricier than their conventional counterparts, and many people still worry about the limited range of all-electrics. If you want to move away from purely petrol-powered vehicles, though, is there any alternative? The four-company Flybus consortium would definitely say there is. It recently rigged up a bus with a prototype flywheel-based energy recover system, that stores the energy that would be wasted when the vehicle brakes, then returns that energy to the drivetrain when the bus accelerates. The researchers claim that it could deliver hybrid-like fuel economy, at a fraction of the price.