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Metro Newsroom

TARC Adds More Hybrid Buses

Friday July 13, 2007

Louisville will breathe easier with the addition of four new hybrid electric buses to TARC’s fleet.

Mayor Jerry Abramson joined U.S. Representative John Yarmuth and TARC Executive Director J. Barry Barker to unveil the additional hybrid buses July 13.

“These hybrid buses show our commitment to clean air,” Mayor Jerry Abramson said. “The buses run quieter than gas-only buses and they emit less pollution.” The hybrid buses also get better fuel economy and have a quieter, smoother ride.

Once these new buses are introduced into service, TARC will have a total of nine hybrids in its fleet. 

The buses cost $504,000 apiece and were made possible with an appropriation from the federal Clean Fuels program obtained by Sen. Jim Bunning. The Kentucky Transportation Cabinet provided the local match through its toll credit program.

The buses will share the design of traditional TARC buses, but will be painted with the same distinctive butterfly design and “Breathe Easier” logo as the five hybrids purchased in 2004. They are 40 feet long and have low-floor access. The hybrid's diesel engine is smaller. A regular diesel bus emits the most pollution when it accelerates from a stop or goes up hill. The hybrid bus uses electric power from its batteries to accelerate, drastically reducing emissions and eliminating tailpipe smoke in these situations. With less demand on the diesel engine, the hybrid buses are much quieter. This innovative bus also accelerates and goes up hills without revving the engine.

Hybrid buses also cost less to maintain, due to brakes that last twice as long, thanks to regenerative braking and no transmission to maintain.

TARC Hybrid Electric Buses: Improving Louisville’s Air

The Transit Authority of River City cares about the cleanliness of Louisville’s air and the health of our community. That’s why we have incorporated Hybrid Electric buses into our fleet. This new technology uses electric power in combination with a diesel-powered engine. It brings many benefits, including lower emissions, better fuel economy and a quieter ride. Next time you see one of TARC’s Hybrid Electric buses pass by you’ll know you can breathe easier.

Caring about air quality

Emissions Reduced:

Oxides of Nitrogen (NOx) – 61% less

Particulate Matter (PM) – 93% less

Carbon Monoxide (CO) – 90% less

Hydrocarbons (HC) – 21% less

Reducing energy consumption

Better fuel economy with an annual savings of 3,000 gallons per bus

High Mechanical performance

Fewer brake repairs necessary

Sixteen times less transmission fluid changes required

No major mechanical errors

Estimated fuel economy

Annual savings of 3,000 gallons per bus

The Hybrid buses have 22% better fuel economy that the majority of TARC buses and 41-57% better fuel economy than the older buses in TARC’s fleet.

For every mile that passengers travel during rush hour, public transit is five times as fuel efficient as private automobiles.

Type of Pollutant (grams per mile)

Hybrid Bus

Average Bus

Emission Reductions

Hydrocarbons (HC)




Carbon Monoxide (CO)




Oxides of Nitrogen (NOX)




Particulate Matter (PM)




Sulfur Dioxide (SO2)




Ammonia gas (NH3)




Maintenance Savings

Since adding Hybrid buses to the fleet, TARC has seen substantial maintenance savings with the new buses. The Hybrid buses are going over 100,000 miles between brake repairs, compared with 75,000 miles between repairs on other buses. The Hybrid buses require 16 times less transmission fluid changes, which saves significant amounts of oil per bus. Since going into service in 2004, there have been no major mechanical errors with the Hybrid buses.

How do they work?

At low speeds, acceleration is more efficiently achieved through the electric motors, but as road speed increase, the Ev Drive blends the electric power with mechanical power. Higher road speeds are achieved through pure mechanical power.

Uses electric motors to accelerate at low speeds, uses Ev Drive to blend electric and mechanical power. At high road speeds, uses pure mechanical power.