Hill start assist control (HAC) explained
On many modern car including many Toyota models come with a feature known as HAC or Hill start assist control. This system is typically available on Automatic models only including the 7-Speed multi-drive automatic that is available in the new generation of the Toyota Corolla Hatch.
This system simply helps to prevent the car from rolling backwards during a hill start. It simply works by the system holding the car briefly in its position when you come off the foot brake and begin to accelerate. Allowing you move off smoothly on those steep hill without rolling, which can be dangerous when there is a vehicle parked behind yours.