The highly popular Toyota Prius continues to garner attention throughout the world, and the 2006 Toyota Prius has been so popular that cars need to be ordered months in advance. The Prius remains primarily unchanged since its redesign in 2004. Changes for 2006 include a rear view camera, new airbags, and a better LCD display. Toyota's Hybrid Synergy Drive system includes a 1.5 liter inline four engine, teamed with two electric motors. The first motor functions as a power generator, for engine startup and battery recharging. The second electric motor drives the front wheels, along with the engine. The total power output is 110 horsepower. The Synergy Drive system is paired with Toyota's continuously variable transmission. The gasoline engine practically lies dormant at city speeds, as the second electric motor powers the car by itself. The EPA estimate for the Prius is 60/51 mpg. Standard features include steering wheel audio and climate controls, a six speaker CD sound system, a trip computer, cruise control, power windows, keyless entry, and automatic climate control. A DVD-based navigation system with voice-activation is an available add-on. Bluetooth and SmartKey are also optional, as is a JBL audio upgrade with nine speakers and an in-dash CD changer.