A Class III Brake Test is necessary when which of the following occurs?

A Class III Brake Test is performed when there is any change made to a locomotive consist. This type of test ensures that all components of the braking system are functioning correctly after adjustments or modifications. Changes to the locomotive consist can include actions like adding or removing cars, altering train configuration, or making modifications to the locomotives themselves. Each of these situations can affect braking performance and safety, so conducting a Class III Brake Test ensures that the entire system is evaluated and remains effective.

In contrast, the other scenarios mentioned do not necessitate a Class III Brake Test under standard operating conditions. For example, testing strictly when a locomotive is new does not address ongoing functionality with existing configurations. Similarly, conducting a test solely while the locomotive is in a maintenance facility or imposing this requirement only for freight trains misses the broader safety considerations applicable to all changes affecting the train's dynamics. Thus, the necessity of the Class III Brake Test is intrinsically linked to changes in the locomotive consist itself.