While backing, you should:

When backing up, turning your head and looking through the rear window is the safest and most effective method. This action provides a clear and direct view of your surroundings, allowing you to spot any obstacles, pedestrians, or other vehicles that might be in your path. Relying solely on mirrors can create blind spots and may prevent you from seeing certain hazards, particularly those close to the rear of your vehicle.

Additionally, while flashing your lights might alert other drivers, it doesn't assist you in seeing behind your vehicle or making informed decisions about the space you are navigating. Opening your door to check safety is not practical, as it can engage you in a dangerous situation, leaving you distracted and possibly exposing you to accidents. Therefore, looking through the rear window accommodates a comprehensive awareness of your immediate environment, making it the most responsible choice when backing up.