What is a primary reason for poor driving conditions during fog?

Reduced visibility is a primary reason for poor driving conditions during fog because fog consists of tiny water droplets suspended in the air, which scatter light and significantly limit the driver's ability to see the road and other vehicles. When visibility is compromised, it can become difficult to judge distances, recognize hazards, or respond appropriately to changes in traffic conditions, leading to an increased risk of accidents.

In contrast, while road construction can indeed lead to poor driving conditions, it is not directly associated with fog. Increased vehicle speed typically exacerbates the dangers of reduced visibility, rather than being a cause itself. Higher winds do not necessarily relate to fog's impact on visibility and can vary independently of fog conditions. Therefore, reduced visibility stands as the key factor in understanding why driving during fog can be particularly hazardous.