2025 Certified Flight Instructor Airplane Practice Exam - Complete Study Guide

The purpose of the yellow demarcation bar marking is to delineate the displaced threshold from adjacent areas. This marking indicates where the runway begins for landing but is not usable for takeoff or landing operations. When approaching a runway with a displaced threshold, pilots must be aware that the area beyond the yellow demarcation bar is not intended for landing, and it helps to clearly communicate the safe and functional area of the runway.

To add context, the other options do not accurately describe the purpose of this marking. For instance, delineating the entrance from a taxiway to a runway typically involves different markings such as solid or dashed lines indicating the taxiway/runway boundaries. The start of a landing runway would be indicated by a different marking, usually the threshold markings, while the end of usable runway would be marked with specific ending markings that identify where the runway no longer supports operations. Therefore, the specific function of the yellow demarcation bar is essential for pilot awareness and operational safety, highlighting the importance of understanding runway configurations.