The auto-enthusiast folks over at PCMag.com have a great article on NYC's new fleet of Orion VII hybrid buses from DaimlerChrysler Commercial Buses. They roll using a 270-hp, 5.9L Cummins diesel as a generator for the array of 46 batteries installed on the roof. The batteries feed a control unit developed by BAE systems and provide the bus with instant torque and seamless acceleration. Plus, since the diesel isn't used as a direct drive component, there's no expensive transmission to maintain. (see illustration after the jump)

While the $500,000 buses do cost some 30-percent more than a traditional diesel bus, they will recoup that loss over the life of the vehicle through lower maintenance costs and less fuel consumed.

So how's the mpg on these things? 3.6 mpg. It doesn't sound like much, but it's a lot more than the current fleet's 2.5 mpg. Each hybrid bus will save 5,000 gallons of fuel a year. The city is purchasing a fleet of 825 buses and together they will save as much fuel as replacing 15,000 passenger cars with hybrids such as the Toyota Prius.  Thus, one hybrid bus equals 18 Priuses.

Check out PCMag.com's very informative slideshow that includes detailed captions about some of the bus's hybrid components.