National Capital Transportation Amendments Act of 2007

National Capital Transportation Amendments Act of 2007 - (Sec. 2) Amends the National Capital Transportation Act of 1969 to authorize the Secretary of Transportation to provide additional funding through grants to the Washington Metropolitan Area Transit Authority (WMATA) to finance in part the capital and preventive maintenance projects included in the Capital Improvement Program. Subjects such grants to specified limitations and conditions. Prohibits funding to WMATA until it notifies the Secretary that certain amendments to the Washington Metropolitan Area Transit Authority Compact have taken effect, including: (1) requiring that all local payments for the cost of operating and maintaining the adopted regional rail system are made from dedicated funding sources (i.e., funding which is earmarked or required under state or local law to be used to match federal appropriations authorized under this Act for payments to the Transit Authority); (2) establishing the Office of the Inspector General of WMATA; and (3) expanding the WMATA Board of Directors to include four additional Directors appointed by the Administrator of General Services.

Prohibits funding to WMATA unless it: (1) provides access to wireless service to rail service customers within the metro system and ensures that each wireless provider of such service has access to the system for upgrades and maintenance; and (2) certifies to the Secretary of Transportation that overtime paid to a WMATA employee does not exceed one-third of the employee's basic rate of pay and that, with respect to a WMATA employee who is separated from employment, such overtime shall be excluded from the annual salary used for determining the employee's retirement annuity. Requires WMATA, not later than one year after enactment of this Act, and each of the three years thereafter, to report to Congress on the implementation of this subsection.

Authorizes appropriations in increments over ten fiscal years beginning in FY2009.

(Sec. 3) Establishes within WMATA the Office of Inspector General. Requires the Inspector General to make specified reports on Office activities: (1) semiannually, to the WMATA Board of Directors and General Manager who shall transmit reports to the appropriate committees or subcommittees of Congress; and (2) annually, to the Governors of Maryland and Virginia, the Mayor of the District of Columbia, and Congress.

(Sec. 4) Requires the Comptroller General to study and report to Congress on the use of funds provided under this Act.