Ind. Code § 8-8-1-6
It shall be unlawful for any common carrier in this state operating an interurban railway by electric power to operate or run upon any railroad in this state any motorcar used in regular interurban passenger traffic which is not equipped with an approved power air brake, in good condition, and subject to the control, and operation of the motorman in charge of such car, and of sufficient capacity to control the speed of the car. It shall also be unlawful for any common carrier, operating a steam or electric railway, and engaged in moving traffic between points in this state, to operate or run upon any railroad in this state any freight or passenger train which is not equipped, as to, at least, as to a steam railroad seventy-five percent (75%), and as to an interurban street railroad fifty percent (50%) of the cars in said train, with an approved system of hand brakes in addition to the power or train brakes required by section 1 of this chapter, which hand brakes shall be kept at all times in proper working condition and of sufficient capacity to control the speed of such train. Provided, that the hand brakes upon every passenger coach, both steam and electric, shall be so constructed that they can be operated in connection with the air or power brakes upon such coach; provided, however, that whenever such power air brakes become disabled from any cause while such car is in service on any such railroad, then, if such car is equipped with a hand brake sufficient therefor, it may complete its run; and, provided further, that this chapter shall not make it unlawful to run such disabled car to the most convenient repair shop upon the road upon which it is then being operated; provided, that this chapter shall not apply to city street railway cars, or cars engaged in suburban traffic.
IC 8-8-1-6