What should you do at least 8 seconds before the locomotive reaches a grade crossing?

Reducing the throttle to RUN 4 or lower at least 8 seconds before reaching a grade crossing is the correct approach because it allows the train to approach the crossing at a controlled speed. This action ensures that the train is prepared to stop if necessary and provides better control of the train's momentum as it approaches a potentially dangerous area where vehicular traffic may intersect the tracks. This technique is crucial for maintaining safety for both train operations and road users.

In operational practice, controlling the speed when approaching grade crossings is essential to avoid accidents and ensure compliance with safety protocols. If the train were to remain at higher throttle settings or increase speed, it would increase the risk of not having adequate stopping distance should any situations arise at the crossing. Thus, a reduction in throttle helps in maintaining a balance of speed with safety.

The focus on safe operations leading up to a grade crossing highlights the importance of proactive measures in train handling and air brake use, especially in areas where passenger safety is a significant concern.