In which situation is it purposeful to use an active lane change assist system?

The combination of 1 and 2 for using an active lane change assist system is correct because these systems are specifically designed to facilitate safe lane changes on high-speed roads like motorways and motorway-like roads. On these types of roads, vehicles travel at higher speeds, and the lane change assist can help monitor blind spots and provide safer maneuvering without needing the driver to check all around manually.

Active lane change assist systems utilize sensors to detect other vehicles' proximity, making them especially beneficial in high-speed environments where changes in traffic occur rapidly. However, on roads without markings (choice 3), such systems may not function effectively, as they rely on clear lane definitions to determine safe distances and driving lines. Therefore, options 1 and 2 represent appropriate conditions for deploying such technology, according to German traffic regulations that emphasize safety and proper vehicle operation under varying road conditions.