How can adverse weather conditions affect traffic signal operation?

Adverse weather conditions can significantly impact the visibility and effectiveness of traffic signals. For instance, rain, fog, or snow can obscure the lights and make it difficult for drivers to see them, which may lead to confusion or misinterpretation of signal indications. When signals are harder to see, their ability to manage traffic effectively diminishes, potentially resulting in increased traffic violations and accidents. Therefore, the correct option points to the direct consequence of poor visibility caused by adverse weather conditions, which can compromise safety and efficiency at intersections.

The other options do not address the immediate and direct effects of weather conditions on the visibility and functionality of traffic signals. While system checks and manual control may be necessary in certain situations, they are not direct consequences of the weather's impact on signal visibility. Additionally, adverse weather does not typically alter the color of the signals themselves; instead, it affects how they are perceived from a distance.