Building Rail Across Intercity Networks To Ride Around Interior of the Nation Act or the BRAIN TRAIN Act This bill directs the Department of Transportation (DOT) to establish an intercity passenger rail service investment program to promote high-performance rail transportation options. DOT may award competitive grants under the program to finance capital projects for high-performance rail, including grants awarded in installments for projects lasting longer than one year. In awarding grants, DOT must select high-performance rail projects (1) that are anticipated to result in significant improvements to intercity rail passenger service, (2) for which there is a high degree of confidence that the proposed projects are feasible and will result in the anticipated benefits, and (3) for which the level of the anticipated benefits compares favorably to the amount of federal funding requested. The federal share of the cost of a capital project shall not exceed 90% of the project's net capital cost.