How many cars must be checked beyond the last applied hand brake?

In the context of air brakes and their operational safety, checking the number of cars beyond the last applied hand brake is essential to ensure that the entire train is secure and has not shifted, particularly when it has been parked. The requirement to check three additional cars serves several critical safety functions.

By checking three additional cars, the crew ensures that not only the immediate vicinity of the last hand brake is secure, but it also verifies that the braking effectiveness propagates through the entire length of the train. This precaution allows for the detection of any potential issues such as slippage or movement in the cars further down the train that may not be immediately visible.

Furthermore, checking this number of additional cars helps to establish a better overall assessment of the train's stability and readiness for departure. It reinforces adherence to safety protocols that help prevent accidents related to uncontrolled movement. As a standard practice within the industry, this procedure is designed to mitigate risks and ensure that all parts of the train are secure before any movement occurs.