A special version of the super small, super stingy Smart Fortwo will be shown at this year's Frankfurt Auto Show. Called the Micro Hybrid Drive, the car's trick feature is its stop/go function to lower emissions and increase gas mileage.
Similar to the systems already in place in cars like the Saturn Vue Green Line and some European-specification BMWs, the Smart isn't a full hybrid, meaning that the car can't move on electric power alone. Instead, this system helps decrease fuel consumption by shutting off the engine in heavy traffic situations. If the driver steps on the brake pedal while the car is moving about five mph or less, the engine automatically shuts off. The motor remains off until the brake pedal is released, at which point it automatically returns to life in a fraction of a second.
The Micro Hybrid Drive is able to start again so quickly because of the use of a belt-driven starter generator. This specialized starter, along with different gear ratios, contributes to about an eight percent fuel savings in mixed driving. In congested city traffic with constant starting and stopping, the feature allows the Smart MHD to achieve about thirteen percent better fuel economy than the comparable gas-engined model without the feature. For those more concerned with quick stoplight getaways than fuel savings, the system can be deactivated by way of a dashboard switch.