What is a requirement for the driver side window?

The requirement that the driver side window should be able to open and close readily is important for both safety and practicality. Drivers must have the ability to open the window for various reasons, such as communicating with pedestrians, allowing fresh air into the vehicle, or in case of emergencies where they need to exit the vehicle quickly. A functional driver side window is essential for proper vehicle operation and ensures that the driver can maintain good visibility and situational awareness.

In contrast, requiring the window to be tinted or remain closed at all times would limit visibility and access to the outside environment, which is counterproductive to the vehicle's safe operation. Additionally, a window that cannot be opened would impair the functionality of the vehicle and could lead to hazardous situations, including difficulties during emergencies. Having a window that operates smoothly contributes to a driver's ability to respond effectively to various driving conditions.