In which situation is it helpful to use an adaptive cruise control system (ACC)?

The combination of using adaptive cruise control (ACC) on motorways and expressways is correct because these types of roads typically allow for high-speed travel with less frequent stops and starts, making ACC particularly effective. The system can help maintain a steady speed and adapt to the flow of traffic, enhancing safety and reducing driver fatigue.

In Germany, traffic laws recognize the use of modern vehicle assistance systems. On motorways (Autobahnen) and expressways (Schnellstraßen), where maintaining speed and distance from other vehicles is crucial, ACC can automatically adjust the vehicle's speed based on the distance to the car ahead, as per regulations aimed at promoting road safety and efficiency.

On winding roads, however, it is generally not advisable to use ACC due to the complexity of conditions, including sharp turns and varying speeds required for safe navigation. Therefore, the combination of options 1 and 2 fully captures the appropriate application of ACC according to German traffic rules.