Hill descent control (HDC, sometimes known as hill mode descent control) is a type of driver assistance system. It enables a controlled slope descent in tough terrain without requiring the driver to apply brakes.
When activated, the car will descend utilizing the anti-lock braking system (ABS) to manage the speed of each wheel. If the car accelerates without driver input, the system will apply the brakes automatically to bring it down to the targeted vehicle speed. The cruise control controls allow you to set the pace to a comfortable level. When the driver applies pressure to the accelerator or brake pedal, the HDC system is overridden.
HDC was first created by Land Rover for use on their Freelander model, which lacks the low range gears typically seen on 4x4 cars. It was criticized by enthusiasts at the time, with many claiming that the fixed speed was too fast for a controlled descent in tough circumstances. Despite the criticism, the system was cutting-edge technology that enabled the Freelander, when combined with the traction control system, to be famous for astonishing off-roading prowess that distinguished it from the so-called "soft roaders" manufactured in the 1990s. Later versions, such as the Range Rover and Discovery, integrate HDC with traction control and low-range gears, as well as lowering the programmed speed to less than walking speed for further control.
Four-wheel drive (4WD) and all-wheel drive (AWD) vehicles, such as Ford Territory, may have a hill descent control system installed, using the ABS to control the car's motion downhill, initially developed by Bosch for Land Rover. The system can be controlled, usually by the cruise control buttons near or on the steering wheel.
Renault / Automobile Dacia has recently added Hillside Decent Control in the second generation of the Dacia Duster, making it the most affordable vehicle in its segment with Hillside Decent Control.