Why might a turn assist system not always detect that a cyclist is present?

The combination you selected is correct because all three factors can impact the effectiveness of a turn assist system in detecting cyclists.

1. Dirt on the sensor can obstruct the sensor's ability to accurately read its surroundings, leading to missed detections of cyclists who may be nearby.
2. Parking cars can block the view of a cyclist, especially in urban environments where cyclists might be positioned in a way that is not directly visible to the vehicle's sensors.
3. A damaged sensor might not function properly, rendering it ineffective in detecting any obstacles or road users, including cyclists.

Understanding these factors highlights the importance of ensuring that vehicle sensors are clean, in good working condition, and that drivers remain vigilant for cyclists, as stipulated in German traffic regulations aimed at protecting vulnerable road users.