Currently, many adaptive cruise control features on the market will slow you down when the car ahead applies the brakes, and it'll speed you up again when things get moving. But usually, at speeds of around 12 mph, the cruise control will deactivate and hand the driving duties back to the human.
Ford's stop-and-go adaptive cruise control, which will be available this spring on new Fusion sedans, works below that speed threshold, and will still function even when your car has come to a full stop. Using a suite of cameras and radar, the technology tracks the car ahead and matches its speed, slowing or even stopping if the situation warrants it.
If you're standing still for more than three seconds, the feature will ask you to tap a button to reactivate it, which could get annoying. Still, so long as the traffic is frequently starting and stopping, so will the car, all by itself.
Read the rest here: https://www.washingtonpost.com/news/the-switch/wp/2016/04/05/ford-just-took-another-step-toward-a-traffic-free-future/