By the way, regarding the need to put up a blue flag while clerks service a caboose. From the GCOR:
5.13 Blue Signal Protection of Workmen
This rule outlines the requirements for protecting railroad workmen who are inspecting, testing, repairing, and servicing rolling equipment. In particular, because these tasks require the workmen to work on, under, or between rolling equipment, workmen are exposed to potential injury from moving equipment. As used in this rule, the following definitions apply:
Workmen. Railroad employees assigned to inspect, test, repair, or service railroad rolling equipment or components, including brake systems. Train and yard crews are excluded, except when they perform the above work on rolling equipment not part of the train or yard movement they are handling or will handle.
“Servicing” does not include supplying cabooses, engines, or passenger cars with items such as ice, drinking water, tools, sanitary supplies, stationery, or flagging equipment.
A clerk sweeping out the caboose or servicing it would NOT REQUIRE a blue flag. It might be local custom but its not required by rule (or by law because if it was required by law the BNSF would have it in their rules.)