RTD aim: less diesel 'bang' for its buck
New hybrid buses promise reduced noise and exhaust
Kevin Flynn, Rocky Mountain News
Published May 31, 2006 at midnight
RTD is putting new hybrid buses into its city fleet to test whether the diesel-electric vehicles can live up to their billing for better mileage, less noise and lower pollution.
Four 40-seat buses, with special exterior paint jobs so riders will know them, will be on the streets by the end of the week.
The buses are powered by a diesel engine equivalent to that of a pickup truck and six storage batteries fed by the power of the engine. They promise to be better in the harsh stop-and-go environment of an urban bus route than the Regional Transportation District's current fleet of regular diesel buses.
"When the driver lets off the throttle, the motor becomes a generator that helps with the stopping," said Chris Collet, of General Motors' Allison Transmission division.
The GM transmissions contain electric drives powered by batteries on the roof of the buses. When the bus pulls out from a stop, it is under electric power, eliminating the belch of diesel noise and exhaust.
The diesel engine kicks in around 11 mph. And from there on, both electric and diesel power propel the bus in an ever-changing mix controlled by an on-board computer.
RTD plans to monitor the buses' performance during the next year to determine whether it should buy more. They are more expensive than regular buses but are less expensive to fuel, maintain and repair.
RTD is paying $297,148 per bus this year for regular diesel-powered Gillig buses. The hybrid model is almost $200,000 more. Whether the lower fuel and maintenance costs override that higher purchase amount is something RTD is eager to learn. RTD already knows, for instance, that the regular buses need oil changes - 30 quarts per bus - every 6,000 miles. But the hybrids can go 18,000 miles between oil changes.
Sen. Ken Salazar attended the unveiling of the buses at Union Station on Tuesday, hailing RTD for taking the step.
"RTD is leading by example here in terms of embracing fuel efficiency," said the Democratic senator.
"The eyes of the nation pretty much are on RTD," Salazar said, noting the agency is beginning its 12-year FasTracks rapid transit expansion as well as experimenting with hybrid buses.
Results in Denver will help determine what other transit agencies do, he said.
"If this test is successful, it will have a big impact on our bus service," said Chris Martinez, RTD board chairman.
On a demonstration ride through downtown, the bus ran much more quietly than regular buses. Its pullout from the curb was swift. The transition from electric to diesel propulsion was unnoticeable to passengers.
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