Unlike cruise control, which typically only works above a certain speed, hill descent control systems are usually designed so that they can only be activated if the vehicle is moving slower than 15 or 20 mph. The specifics vary from one automaker to the next, but it is generally a low-speed technology.
Hill descent control typically works in a multi-step process:
Like many other automotive safety features and advanced driver assistance systems, hill descent control automates a task that a driver would typically have to do manually. In this case, that task is controlling the speed of a vehicle on a downslope without losing traction. Drivers usually accomplish that by downshifting and tapping the brakes, which is also the same basic method utilized by hill descent control systems.