What is a common requirement for traffic cones when used in low visibility conditions?

In low visibility conditions, the primary goal is to ensure that traffic cones are easily seen by drivers to maintain safety on the road. The correct answer emphasizes the application of reflective sheeting, which enhances the visibility of the cones in numerous situations, such as nighttime or during inclement weather. Reflective sheeting works by reflecting headlights, making the cones stand out to approaching vehicles, thereby helping to alert drivers and directing them safely around incidents or construction zones.

While options such as the use of LED lights or sound devices may contribute to visibility and alertness, they are not as universally required or commonly implemented as reflective sheeting. Moreover, the placement of cones on flat surfaces is more about stability and effectiveness rather than visibility in low-light conditions. Thus, reflective sheeting remains the most reliable method to ensure that traffic cones are perceptible in such challenging environments.