The CTA is testing a new hybrid electric bus that can get seven to eight miles per gallon -- double the mpg of current CTA hybrids.
The new hybrid engine uses batteries to run an electric motor which runs the bus. The current hybrids use a diesel engine to power the bus, with the help of an electric motor.
When batteries lose power on the new electric hybrid, a small turbine engine, powered by diesel, propane or compressed natural gas, turns on to recharge the batteries. The CTA claims this configuration produces lower emissions than other hybrids and reduces noise pollution.