What is an essential characteristic of traffic cones used during nighttime operations?

Reflectivity is an essential characteristic of traffic cones used during nighttime operations because it significantly enhances visibility in low-light conditions. Traffic cones that incorporate reflective materials ensure that they can be easily seen by drivers, even in the dark or in poor weather conditions. This feature is crucial for maintaining safety in work zones at night, as it helps to alert drivers to potential hazards, guiding them to navigate safely around the area.

While size, color, and shape are all important design elements for traffic cones, they do not address the specific visibility challenges presented at night. The reflectivity of a cone is what enables it to stand out against the dark background, reducing the likelihood of accidents and improving overall safety for both workers and motorists. Thus, for nighttime operations, reflectivity is the most critical characteristic of traffic cones.