Which action completes the 11-3 crossover sequence?

• A. Finish throwing frog
• B. Move the middle switch first
• C. Halt and wait for instruction
• D. Set the first switch only

Answer: (A)

In a crossover sequence, the safety and progression depend on making sure the turnout components end in their final, locked positions so the track path is fully aligned for the next train. The key step is finishing the throwing of the frog—the crossing piece where the rails actually intersect. When the frog is fully moved into its intended position, the rails line up correctly and the wheel paths establish a safe, continuous surface for crossing from one track to the other. If you only start or partially complete actions—like moving a middle segment first, or setting just the first switch, or halting to wait for instruction—you leave the crossing in an intermediate, unstable state. That partial positioning can create gaps or misalignment that increase the risk of derailment or wheels tracking onto the wrong rail. Completing the frog movement finalizes the crossover, making the route safe and ready for use.