During the 2011 Society of Automotive Engineers World Congress, General Motors presented an outline for its new prototype two-mode transmission designed specifically for upcoming front-wheel-drive plug-in hybrid vehicles.
The transmission will feature two electric-only modes — named EV1 and EV2 — that allow the vehicle to drive in urban and highway settings using only electricity. EV1 handles the lower speeds, while EV2 makes it possible for electric driving at highway speeds, assuming there is a sufficient amount of battery power. Otherwise, the transmission will utilize its engine operating modes.
Source: Green Car Congress