To ensure safe driving, it is essential that the **vehicle's lights function correctly**. When the protective covers of the lights are dirty, the **effectiveness of the lights decreases**. This is because dirt prevents the light from being properly projected, reducing visibility for both the driver and other road users.

- **Visibility while driving**: It is essential to keep all glass and light surfaces clean to ensure good visibility. Dirt on the light covers can obstruct the light, making the road and surroundings less visible.

- **Proper use of lights**: Lights should be on in low-light conditions, such as at night or on dark days. If the lights are dirty, their ability to illuminate properly is compromised, which can be dangerous.

- **Glare**: Although keeping the lights clean is not directly related to avoiding glare, it is important that the lights are well-adjusted and clean so as not to affect the visibility of other drivers.

In summary, keeping the light covers clean is crucial to ensure that the lights function effectively and provide the necessary visibility for safe driving.