The GMC Terra4 has a closed body and a short, deep cargo area. Its most distinctive attribute, however, is what makes it go. The Terra4 is derived from GM's Parallel Hybrid Truck, which unites a 285 horsepower, 5.3-liter Vortec V8 gasoline engine with an electric motor and generator. The motor-generator gives the Terra4 enough power to start and generates electricity when the vehicle decelerates. At a stoplight, the gas engine shuts off but the accessories continue working on stored electrical power. When the driver accelerates, the gas engine restarts automatically.