Most hybrids currently all have the idle-stop technology when the car is not moving. When the driver engages the clutch and releases the brake, the electric motor or battery jump starts the engine. My question is why is this technology only applied when the car is not moving? Why not have idle-stop kill the engine whenever the clutch is pushed down, and the engine is not engaged even when the car is moving, i.e. going down hill. Is this not done purely on a safety concern? Or is there some technology speed bump that havent been resolved yet?