What is the purpose of the triangular window on a car?

[Emilia]

The functions of the triangular window on a car are: 1. Expanding the field of vision and reducing blind spots. The triangular window on the front door can enhance the driver's field of vision, while the one on the rear door increases the viewing area for backseat passengers, providing them with a broader view. 2. The triangular structure offers greater stability. The presence of the triangular window ensures smoother operation when rolling the window up and down, and it also reduces the manufacturing difficulty of the window mechanism. 3. Assisting in judging the vehicle's position. Drivers can clearly see the position of the wheels through the triangular window, helping them determine the direction of the wheels when turning. Many car owners apply window films after purchasing a car, and those who prioritize privacy may even add an extra layer to the windows. However, no one applies film to the triangular window. According to regulations, the triangular window on the front door must not be covered with film, as doing so would impair the driver's visibility.