The Railpower GG20B Green Goat is a low-emissions diesel hybrid switcher locomotive built by Railpower Technologies Corp. It is powered by a single Caterpillar C9 six cylinder inline engine developing 300 horsepower (224 kW), which is also connected to a large battery bank where both sources combine for a total power output of 2,000 horsepower (1,490 kW). To date, there have been more than 50 GG20B diesel-electric hybrid switchers manufactured since their first introduction in 2004.

A hybrid train is a locomotive, railcar or train that uses an onboard rechargeable energy storage system (RESS), placed between the power source and the traction transmission system connected to the wheels. Since most diesel locomotives are diesel-electric, they have all the components of a series hybrid transmission except the storage battery, making this a relatively simple prospect.