What materials are runway markings made of?

Runway markings are primarily made of paint that incorporates retroreflective glass beads or preformed materials. This choice is correct because runway markings need to be highly visible both during the day and at night, which is where the retroreflective glass beads come into play. These beads reflect light back toward the source, enhancing visibility for pilots as they approach landing and during takeoff.

The use of paint is standard for runway markings because it can be applied in specific patterns and colors needed for effective communication to pilots. Preformed materials are also utilized in some applications because they can offer durability and consistent visibility over time without frequent reapplication.

Other materials listed do not meet the specific requirements for runway markings. Plastic and metal composites, for example, are not suitable for runway applications due to the need for flexibility and the specific properties of paint that allow for proper adherence and visibility. Similarly, rubber and synthetic polymers would not provide the necessary durability and visibility characteristics needed for runway markings. Finally, concrete surfaces serve as the structural base but do not function as markings themselves. Therefore, the choice referencing paint with retroreflective glass beads or preformed materials is the correct response for materials used in runway markings.