Only in case of 100 meters visibility from both sides
In case of creating an obstacle
In neither case✓Правильный ответ
Объяснение
The English prompt diverges from the source editions: they ask about a U-turn after the sign, and the accepted source response allows it under neither stated condition. The square blue sign marks one-way travel, so turning around would place the vehicle against the permitted flow regardless of visibility or an obstruction.
