It is very important to note that most present-day CVT's drive with a friction element. Unlike gears that can be produced with any size necessary for the torque load they must transfer, CVT's are limited in torque capacity and are only marginally suitable for small vehicle applications. A system is described using two variable-inertia flywheels to not only supply the heavy torque requirements during acceleration of a vehicle but also operate in reverse capturing the otherwise wasted decelerating torque (I.E. braking torque). This system (called Kinetic Energy Power Transmission System or KEPTS) provides all of the documented benefits of the use of an IVT for motor vehicle acceleration and also incorporates regenerative braking. The significance of the system is that besides providing a complete KERS (kinetic energy recovery and storage) system, all accelerating and braking torque is provided by the two variable-inertia flywheels, thus allowing the main motive engine (ICE, electric traction motor, gas turbine, etc.) to operate at a fixed angular velocity (rpm) isolated from large torque variances, and the CVT elements can be minimized in size (I.E. low-torque).
Mechanical (flywheel) kinetic energy storage is a formidable contender for regenerative braking systems and this is particularly the case for ICE (internal combustion engines) where few alternatives exist. Regenerative braking should be aggressively pursued for those vehicles with a rapid driving cycle (frequent start-stop cycles). The competing technology for all-electric vehicles is ultra-capacitors. When flywheel technology is implemented with an efficient, high-torque infinitely-variable transmission (IVT) a high percentage of the vehicle kinetic energy normally lost to friction braking systems can be returned to the vehicle during a brake-stop-launch cycle. Overall fuel use is then primarily determined by rolling resistance and air drag.