STA Hybrid Facts
Spokane Transit Hybrid Coaches
Spokane Transit’s initial purchase of three 40-foot Gillig diesel-electric hybrid buses was part of a larger joint purchase by the San Joaquin Regional Transit District. They were delivered in late October 2007. This “piggyback” purchasing technique allowed STA to buy them for less than if the coaches were purchased separately. The total cost for the initial three hybrids (including tax and delivery” was $1.76 million. A federal grant provided 80 percent of the funding to purchase the first three hybrids in the fleet. Spokane Transit purchased six more 40-foot hybrids in 2008, then more in 2010, and replaced three downtown shuttle replica trolley streetcars with three 30-foot hybrids in 2009 – bringing the current total number of operating diesel-electric hybrids in the STA flee to 22.
A hybrid coach looks similar to a regular diesel coach except for a large area on the top of the bus that holds the battery pack for the drive systems and some subtle livery markings to distinguish it from a standard coach.
- The GM drive system is similar to other hybrid vehicles in that it uses a blending of diesel and electric power – but is different than most passenger vehicle systems because the diesel engine must idle at all times to operate the power steering and other accessory systems such as air-conditioning.
- When driving less than 10 miles per hour, the hybrid buses use the low-torque power from the electrical drive system to move the vehicle. To sustain higher speeds, the hybrids must use the power generated from the diesel engine. This “blending” is controlled by an onboard computer that uses an extensive series of sensors to accelerate the diesel engine and manage power transition.
- The electrical drive unit (the “e-drive”) takes the place of the transmissions in the drivetrain. The power to engage and accelerate the vehicle from a stop is delivered to the e-drive by a large insulated cable that can deliver as much as 900 volts from the battery pack located on the top of the vehicle.
- The drive system uses an automatic traction control system like most new traditional diesel-powered buses, but the braking system also serves as a generator to recharge the batteries. This “regenerative braking” makes the vehicle slow down faster than a regular diesel-powered bus when not under acceleration.