What does sign Q6 indicate about the obstacle ahead?

Sign Q6 indicates that there is a narrow road ahead where only one vehicle can safely pass through at a time. This means that the road narrows to the extent that two vehicles cannot pass side by side without risking a collision or obstruction. Drivers should proceed with caution and be prepared to yield to oncoming traffic or any obstacles in order to navigate through safely.

In this context, the other options do not accurately reflect the intention of the sign. For example, the notion that two vehicles can pass side by side contradicts the premise of the sign indicating a narrow passage. Similarly, the options suggesting that all vehicles must stop or that no vehicles are allowed do not align with the indication of a specific road condition; rather, they imply restrictions that are not applicable to this scenario. The key takeaway from sign Q6 is the limitation on space, making the indication of a single vehicle being able to pass through correct.