Fouling points are indicated by:

• A. Yellow stripe painted on the inside and outside of head, web, and base of both rails
• B. Sign displaying the letters 'FP'
• C. Fixed derail
• D. Yellow flag attached to switch stand

Answer: (B)

The fouling point is the exact location where a train or its cars begin to foul an adjacent track, so crews need a clear, standardized marker to know where that limit is. A sign displaying the letters “FP” is the standard indicator used to mark that point. It communicates to yard workers and locomotive crews where they must not allow equipment to extend beyond on the neighboring track during moves or switching.

The other options aren’t the formal indicator for a fouling point. A yellow stripe on the rails is a general caution marker used for various purposes and isn’t the official fouling-point sign. A fixed derail is a safety device placed to prevent entry onto a track, not a marker for where fouling occurs. A yellow flag at a switch stand indicates flag protection for a switch or work area, not the fouling point marker.