Final answer:
Limited visibility is defined as the inability to see people or vehicles clearly less than 100 meters away, during one-half hour before sunset to one-half hour after sunrise, and in poor light conditions such as fog, snow, or rain.
Step-by-step explanation:
Times of limited visibility on roads are crucial for the safety of drivers and pedestrians. According to traffic safety rules, such times are typically defined as being one-half hour before sunset to one-half hour after sunrise, as well as during weather conditions that cause poor visibility. Such conditions could include fog, heavy snow, or intense rain. These conditions can severely reduce a driver's ability to see other vehicles or people on the road.
Given the need to ensure safety, the specific answer to the question would be that limited visibility is considered to occur when people or vehicles cannot be seen clearly at a distance less than 100 meters away. This distance allows drivers enough time to react to any potential hazards that emerge within their line of sight, thereby reducing the risk of accidents.