What factor has been identified as the most significant in making pedestrians easy to see?

While effective warning lights are indeed essential for drawing attention, particularly in low visibility conditions, the factor identified as the most significant in making pedestrians easy to see is actually the type of clothing they wear. High-visibility clothing, especially those with reflective elements, increases a pedestrian's visibility dramatically, particularly in conditions of reduced light, such as dusk or dawn. Wearing brightly colored or reflective clothing allows pedestrians to be more easily distinguished from their surroundings, thereby enhancing their safety.

The context of other options further supports this understanding. Effective warning lights are important but are designed to attract attention to vehicles rather than pedestrians themselves. Reflective surfaces can aid in visibility by bouncing light back toward its source, but this is typically more effective on the clothing of pedestrians than as a standalone factor. The time of day, while relevant to visibility conditions, does not directly contribute to the pedestrian's visibility in the same way that their clothing does. Hence, it’s the type of clothing that stands out as the most significant factor for pedestrian visibility.