((a)) ** .—** Except as provided in subsection (c) of this section and , a railroad carrier may use or allow to be used on any of its railroad lines—

((1)) a vehicle only if it is equipped with—

((A)) couplers coupling automatically by impact, and capable of being uncoupled, without the necessity of individuals going between the ends of the vehicles;

((B)) secure sill steps and efficient hand brakes; and

((C)) secure ladders and running boards when required by the Secretary of Transportation, and, if ladders are required, secure handholds or grab irons on its roof at the top of each ladder;

((2)) except as otherwise ordered by the Secretary, a vehicle only if it is equipped with secure grab irons or handholds on its ends and sides for greater security to individuals in coupling and uncoupling vehicles;

((3)) a vehicle only if it complies with the standard height of drawbars required by regulations prescribed by the Secretary;

((4)) a locomotive only if it is equipped with a power-driving wheel brake and appliances for operating the train-brake system; and

((5)) a train only if—

((A)) enough of the vehicles in the train are equipped with power or train brakes so that the engineer on the locomotive hauling the train can control the train’s speed without the necessity of brake operators using the common hand brakes for that purpose; and

((B)) at least 50 percent of the vehicles in the train are equipped with power or train brakes and the engineer is using the power or train brakes on those vehicles and on all other vehicles equipped with them that are associated with those vehicles in the train.

((b)) ** .—** A railroad carrier complying with subsection (a)(5)(A) of this section may refuse to receive from a railroad line of a connecting railroad carrier or a shipper a vehicle that is not equipped with power or train brakes that will work and readily interchange with the power or train brakes in use on the vehicles of the complying railroad carrier.

((c)) ** .—** Notwithstanding subsection (a)(1)(B) of this section, when vehicles are combined to load and haul long commodities, only one of the vehicles must have hand brakes during the loading and hauling.

((d)) ** .—** The Secretary may—

((1)) change the number, dimensions, locations, and manner of application prescribed by the Secretary for safety appliances required by subsection (a)(1)(B) and (C) and (2) of this section only for good cause and after providing an opportunity for a full hearing;

((2)) amend regulations for installing, inspecting, maintaining, and repairing power and train brakes only for the purpose of achieving safety; and

((3)) increase, after an opportunity for a full hearing, the minimum percentage of vehicles in a train that are required by subsection (a)(5)(B) of this section to be equipped and used with power or train brakes.

((e)) ** .—** In carrying out subsection (d)(2) and (3) of this section, the Secretary may use the services of the Association of American Railroads.