It works on any type of road since it would follow the traffic in front without user input. The car stops if the car in front stops and starts when the car in front starts:
There are loads of other videos online. I did some researching into this a little while back. Cheap system overall and many cars are fitted with it. 15-20000$ cars for now but give it 3 years and you will see it stock on the Renault Clio :P
Im sure you are referring to adaptive cruise control