By Ted Evanoff, Star Detroit Bureau, November 10, 2001

Although cars and trucks in the United States nearly outnumber the people, a sure way to help cut down on city smog is to retool one of the smaller fleets on the roads -- smoky diesel buses. Allison Transmission's electric-vehicle think tank in northeast Indianapolis could start clearing urban smog by mid-decade with its electric solution. Replacing the hefty diesel engine with a slimmer model hooked to sizable electric motors would power the 20-ton buses just like environmentally friendly cars such as Toyota's 52-mile-per-gallon Prius. Buses equipped with Allison's diesel-electric system won't match Prius' mileage, but bus fuel economy could improve 60 percent, reducing smog and related respiratory ailments as buses burn fewer gallons of diesel oil.

Allison Electric Drive, as the 150-employee operation in the Castleton area is called, next spring will roll out an advanced version of its experimental diesel-electric powertrain for the 40-foot passenger buses that constantly stop and go on urban streets. The new system pairs a 5.9-liter Cummins diesel engine with a pair of electric motors in a union known as a hybrid electric. Hybrid refers to the two separate powerplants -- diesel and electric.

With a national discussion under way about reducing oil imports from the volatile Middle East in the wake of the terrorist attacks, Allison appears positioned as one of the few major enterprises in the nation on the verge of bringing out a fuel-saving powerplant. After testing the hybrid for three years on a handful of trucks and buses, Electric Drive next year intends to build 40 models under its Preview program. "We've left the R and D stuff, and we're getting real with it now," said Larry Nitz, Allison's chief engineer for controls and advanced engineering. R and D stands for research and development. Electric Drive has set up its own marketing arm in anticipation of selling buses to urban fleets by mid-decade.

New Flyer Co. of Winnipeg, Manitoba, the continent's largest transit bus maker, has ordered a portion of the 40 vehicles, which could open the way for future sales as the bus makers book orders for hybrid buses with city fleets. Although early-generation hybrid test buses from Allison and other companies are in city fleets now, Allison's Preview program buses are second-generation models. They differ because they are equipped for high-speed highway commutes as well as low-speed stop-and-go routes. Test hybrids in the city fleets now chiefly are designed for the low-speed routes. Allison also is discussing potential sales of Preview buses with bus maker Gillig Corp. of Hayward, Calif., as well as with New York City for a garbage truck powered by a hybrid.

Allison has doubled the size of the Electric Drive staff in the past year, bringing in engineers and scientists as it honed its Preview drive train. Engineers harnessed a 5.9-liter Cummins diesel to Allison's electric drive system. It unites a pair of electric motors and an electronic brain with the diesel. A favored claim among electric-drive proponents says if the nation's 10 largest cities converted their bus fleets to diesel hybrids, the effect on the air would be like replacing 500,000 conventional cars with hybrid electric vehicles such as the Toyota Prius and Honda Insight.

Nitz, an electrical engineer who came to Electric Drive in 1997 from GM's Saturn small-car enterprise, sees no reason to dispute the statistic. City buses in operation nationwide number only in the thousands -- about 7,000 are built each year in North America. But the buses run night and day, almost every day of the year. Whether the bus is rolling or stopped to dispatch passengers, the engine runs, spewing exhaust into the atmosphere. In the hybrid version, an electronic brain shuts off the diesel when the bus stops. The electric motor powers the interior heating and cooling systems. When the driver accelerates away from the stop, the diesel turns on. And the electric motor lends a shoulder, sending power to turn the wheels. Friction from braking generates power for the motor.

In an earlier hybrid, Allison paired a chunky 11-liter Cummins diesel generating 285 horsepower with Allison's patented EV Drive, an electric motor system producing 3,000 foot-pounds of torque. Torque is the pull-away power, when, for example, the vehicle pulls away from a stop. To help improve fuel economy, the next-generation hybrid developed for the Preview program mates the 5.9-liter Cummins with an improved EV Drive generating 4,000 foot-pounds of torque. The result is a 60 percent improvement in fuel economy over the typical city bus' 3.5 mpg. The 11-liter diesel hybrid improved mileage 50 percent. For the Preview program, Electric Drive has enough room for production in its Castleton facility and at Allison's complex in Speedway. The company isn't discussing where it might build hybrids in higher volumes.

Contact Ted Evanoff at 1-313-417-9215 or via e-mail at ted.evanoff@indystar.com