Vehicles have started coming to market using the new GM/Chrysler/BMW "Two-Mode" hybrid system. I see this system mentioned as both Dual Mode and Two-Mode in various places. Unlike the traditional serial hybrid, the GM/Chrysler/BMW can connect the shaft of the generator to the shaft of the traction motor by way of a clutch. This would apparently offer an efficiency boost when cruising at highway speeds on ICE power (although they tend to use a very large ICE with this system). GM says this: " The two-mode hybrid system GM’s two-mode full hybrid system in transit buses has been established as the starting point for the GM-BMW-DaimlerChrysler collaboration. The design integrates proven automatic transmission technology with a patented hybrid-electric drive system to deliver the world’s first two-mode full hybrid. The two-mode is patented hybrid technology with two modes optimized for city and highway driving. In the first mode, at low speed and light loads, the vehicle can operate in three ways: electric power only, engine power only or in any combination of engine and electric power. When operating with electric power only, it provides all the fuel savings benefits of a full hybrid system. Leaving the engine shut off for extended periods of time and moving under electric power at low speed is key to reducing fuel consumption in heavy stop and go traffic. The second mode is used primarily at highway speeds. In addition to electric assist, the second mode provides full eight-cylinder engine power when conditions demand it, such as when passing, pulling a trailer or climbing a steep grade." Automobile magazine gave it a "Technology of the Year" award saying: "General Motors' Two-Mode hybrid system is the most significant gasoline-electric propulsion advancement since the original Toyota Prius. Chevrolet Tahoes and GMC Yukons equipped with this technology can achieve 20 mpg or more, which is equivalent to that of a four-cylinder mid-size sedan in city driving. With oil approaching $100 per barrel and a trip to the pumps capable of inflicting a like-size dent in your wallet, big trucks that don't guzzle gas on an ordinary commute seem like manna from the Middle East. To celebrate their arrival, we're saluting GM's Two-Mode as Automobile Magazine's 2008 Technology of the Year. Like Honda's Integrated Motor Assist and Toyota's Hybrid Synergy Drive, Two-Mode blends the best attributes of internal combustion and battery-powered electric motors. But that's the only thing these three prevailing hybrid systems have in common. GM's hybrid powertrain consists of a husky 332-hp, 6.0-liter V-8 bolted to what looks like an overgrown automatic transmission. Actually, that box (pictured above) is packed with the following hybrid components: two 80-hp AC motors; three planetary gear sets; four multiplate clutches; two hydraulic oil pumps. A metal container located under the second-row seats contains the 300-volt nickel-metal hydride battery pack. A second box mounted under the hood is loaded with power inverters and control circuits."