Metro Accountability and Investment Act This bill authorizes additional funding to the Department of Transportation (DOT) to provide grants to the Washington Metropolitan Area Transit Authority (WMATA) for capital and preventive maintenance projects. DOT may not provide such grants until it annually certifies that the Board of Directors of WMATA has passed a resolution, and is making progress implementing such resolution, that establishes an independent budget authority, procurement authority, and independent hiring authority for the Office of Inspector General of WMATA; ensures the inspector general can obtain legal advice from a counsel reporting directly to the office; and requires the inspector general to submit recommendations for corrective action to the General Manager, the board, and Congress, and to publish any recommendations on the office's website, with redactions to prevent security risks. DOT may provide additional grants to WMATA for the purpose of funding the capital and preventive maintenance projects included in the Capital Improvement Program approved by the board.