Marginal Railroad Main Line Service Assurance Act of 1979

Marginal Railroad Main Line Service Assurance Act of 1979 - Amends the Railroad Revitalization and Regulatory Reform Act of 1976 to authorize the Secretary of Transportation to provide assistance to railroads for the purpose of maintaining marginal main line railroad operations which would not be otherwise included by a bankrupt railroad as part of a plan for reorganization. Stipulates that such assistance may not exceed 70 percent of the costs of maintaining operations on a marginal main line.

Stipulates that in order to be eligible for such assistance: (1) the line must be presently operated by a rail carrier under bankruptcy reorganization and be unlikely to survive such reorganization or be saleable; (2) the region served by such a line is without reasonable rail alternatives; (3) the line is unlikely to be approved for abandonment by the Interstate Commerce Commission under present abandonment criteria; (4) continuation of service over such line is essential; (5) the line may be potentially viable; and (6) the loss of such line would result in more than a 15 percent annual increase in Federal-State highway expenditures.

Stipulates that the Secretary must make an annual determination regarding a line's eligibility to receive assistance.

Sets forth procedures for the repayment of such assistance in the event the line returns profits the provisions of this Act.