Gliding (vehicle)

Gliding is an energy-efficient driving mode achieved by turning off the internal combustion engine while the vehicle is still moving in order to save fuel. This is differentiated from coasting, which means running the vehicle in idle mode by disengaging the engine from the wheels, either by disengaging the clutch or setting the transmission or gearbox to neutral position.^[1] Gliding and coasting use the accelerated kinetic energy reserve stored in the vehicles mass, i.e. inertia, to keep the vehicle moving. This energy, however, is being lost due to forces that resist movement, such as air-drag, rolling resistance and gravity. The functionality, being an integral concept of hybrid electric vehicles, is performed automatically by the engine controller. For vehicles with a conventional internal combustion engine, coasting can be performed manually; gliding requires having a gear box.^[2] Manual gliding or coasting is illegal in some states. An extra button to stop the engine was shown in 1979 on International Motor Show Germany,^[3] but never became a feature in mass production of any vehicle. In 1980 research was made on the IRVW II. A so-called eClutch (electronic controlled clutch) uses an actuator to disengage the clutch when the driver releases the accelerator.^[4]

A start-stop system turns the engine off when the vehicle is stopped. Gliding is turning off the engine while the vehicle is still moving. Safety relevant components like power steering or vacuum servo might be required to be electrically powered, but in most vehicles these components are driven by the combustion engine, only. The fuel saving is depending more on the road terrain and traffic conditions. It is assumed to save up to 7% fuel in the NEDC driving cycle; in real road traffic conditions, the savings is estimated to be up to 10%.