Rail Infrastructure Development and Expansion Act for the 21st Century

Rail Infrastructure Development and Expansion Act for the 21st Century - Amends Federal rail transportation law to authorize the Secretary of Transportation to designate bonds if: (1) the bonds are issued by a State, or one or more of the States that have entered into an interstate compact under the Amtrak Reform and Accountability Act of 1997, or by such compact; (2) such bonds are for financing projects to provide a major portion of the infrastructure required to complete a railroad passenger transportation corridor for high-speed intercity rail passenger service, or for projects for the Alaska Railroad; (3) for a railroad passenger transportation corridor design that includes the use of freight railroad rights-of-way, a written agreement exists between the applicant and the freight railroad regarding such use and other conditions are met; (4) the corridor design eliminates all existing railroad grade crossings and requires no additional railroad grade crossings to be created; and (5) the applicant agrees to comply with certain labor standards with respect to such project. Excludes the interest on such bonds from an individual's gross income.

Makes corridor development activities (including the acquisition of locomotives, rolling stock, track, and signal equipment) eligible for Federal assistance.

Amends specified Federal law to change from discretionary to mandatory the Secretary's authority to provide direct loans and loan guarantees for rail rehabilitation and improvement projects to State and local governments, interstate compacts, government sponsored authorities and corporations, railroads, and joint ventures that include at least one railroad.