What air test is required on the remaining consist after setting out the locomotive?

The correct answer is that no air test is required after setting out the locomotive. This is because when a locomotive is cut away from the remainder of the train, the consist is still considered to be intact and not a new train. Therefore, the air brake system remains operational as it was previously tested while still connected. Any air tests required are typically associated with initial setups or after certain maintenance procedures, but simply removing a locomotive does not trigger this requirement.

This approach ensures efficiency since conducting an unnecessary air test after a locomotive removal could slow down operations without adding safety value, as long as the brakes on the remaining cars were previously tested and found compliant.