In the process of securing a train, what is the final step to ensure it is secure?

The final step to ensure a train is secured involves making a 20 psi brake pipe reduction. This action is crucial because it initiates the application of the air brakes, ensuring that they are set and will hold the train in place. By creating a reduction in the brake pipe pressure, the brakes on the train cars are activated, providing a necessary safety measure to prevent any unintended movement.

In the context of securing a train, having the air brakes engaged correctly serves to keep the train stationary, which is vital for safety during loading and unloading operations, or when the train is left unattended. This step confirms that the braking system is fully operational and contributes to the overall security of the train.