When is a locomotive air brake test required on multiple-unit consists?

A locomotive air brake test is required on multiple-unit consists when rearranging locomotives in a consist because this action can affect the overall air brake system. Each locomotive in a consist may have different braking capabilities, and rearranging them can alter how the air brakes interact. By performing a brake test after such a change, the crew ensures that all braking systems are functioning effectively together, which is crucial for safety when the train is in operation.

When locomotives are moved around, there is potential for discrepancies in pressure or function between different units. Therefore, an air brake test validates that all components are properly synchronized and ready for operation. This ensures compliance with safety regulations and helps prevent accidents that could arise from improper functionality of the brakes after the rearrangement.