Metro Accountability and Investment Act This bill amends the Passenger Rail Investment and Improvement Act of 2008 to authorize additional funding to the Department of Transportation (DOT) for grants for capital and preventive maintenance projects for the Washington Metropolitan Area Transit Authority (WMATA) in increments over 10 fiscal years beginning in FY2020 or until expended, subject to specified limitations. DOT may not provide such grants until it 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 for the Office of Inspector General of WMATA, an independent procurement authority for such office, and an independent hiring authority for such office; 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 recommendation on the office's website, with redactions to prevent security risks.. DOT may make 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.