What aspect of traffic control devices affects their visibility?

The visibility of traffic control devices is significantly influenced by their placement and the type of reflective materials used. Proper placement ensures that the devices are seen where they are most needed, allowing them to effectively capture the attention of drivers and pedestrians. Additionally, the use of high-quality reflective materials enhances visibility, especially in low-light conditions or during nighttime. These materials reflect light back towards the source, making the devices stand out and ensuring that they can be seen from a distance, improving safety on the roads.

While factors such as color, size, and light exposure may play a role in visibility, they do not have the same direct impact as the combination of effective placement and the appropriate use of reflective materials. Therefore, focusing on these two aspects is critical for ensuring that traffic control devices fulfill their intended purpose of guiding and warning road users effectively.