Which engine's number will be illuminated when multiple engines are coupled?

The correct answer indicates that when multiple engines are coupled, the number of the leading unit, when practical, will be illuminated. This choice is appropriate because identifying the leading engine is crucial for operational clarity and communication among crew members, particularly for the purposes of signaling and locomotive control.

Having the number of the leading engine illuminated aids in ensuring that anyone involved, including ground personnel and train crews, can quickly and accurately identify the front of the train, enhancing safety and efficiency during operations. In scenarios involving emergency responses, maintenance, or operational communications, knowing which unit is leading becomes vital.

The leading unit typically controls the air brakes for the entire train, making its identification even more significant. Additionally, while it’s conceivable that other units could be illuminated, the emphasis on the leading engine aligns with practices aimed at establishing a clear understanding of train dynamics and authority within team operations. This choice reflects the standard practices in locomotive operations within the BNSF framework for ensuring clarity and proper functioning of train movements.