For years, owners of the gas-electric hybrid Toyota Prius have enjoyed cruising around in full-electric mode at low speeds. Hybrid hobbyists call this the stealth mode, since its silent operation can startle pedestrians not aware that a car is approaching them. Some hobbyists in North America have even modified their vehicles so that their cars will stay in full-electric mode at the flip of a switch (a feature that comes standard in European models of the Prius).
Stealth mode has caught the eye and ear of the Department of Defense. The U.S. Army Tank-Automotive Research, Development and Engineering Center in Warren, Michigan has developed prototype hybrid electric Humvees that can operate in silent mode on batter power alone.
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A Hummer That Really Hums
