Introducing PSTA's new environmentally friendly hybrid bus called the Smartbus. PSTA now has 24 diesel electric hybrid buses on the road. A hybrid bus has an electric motor built right into the transmission. A special battery pack is used to power the motor, which is responsible for starting the bus from a stop. As the bus picks up speed, a special computer seamlessly adds power from the diesel engine until the diesel engine takes over completely at higher speeds. This makes the buses quieter and more fuel efficient than conventional diesel vehicles. Because they have an electric drive as well, the actual diesel engine in a hybrid bus is about the same size as one you would find in a large pickup truck.
Slowing a hybrid bus is also done differently than in conventional vehicles. When the driver takes his or her foot off the accelerator, the motor in the transmission acts like a generator, which slows the bus while simultaneously charging the battery pack. This process is known as "regenerative braking" and has been proven to greatly reduce the need for costly brake repairs and replacement.