49 CFR 230.70: Safe condition.

(a) Pre-departure inspection. At the beginning of each day the locomotive is used, the steam locomotive operator shall ensure that:

(1) The brakes on the steam locomotive and tender are in safe and suitable condition for service;

(2) The air compressor or compressors are in condition to provide an ample supply of air for the locomotive service intended;

(3) The devices for regulating all pressures are properly performing their functions;

(4) The brake valves work properly in all positions; and

(5) The water has been drained from the air-brake system.

(b) Brake pipe valve required. Each steam locomotive shall have a brake pipe valve attached to the front of the tender, the rear of the back cab wall, or adjacent to the exit of a vestibuled cab. The words “Emergency Brake Valve” shall be clearly displayed near the valve.