The Southern Pacific and Rock Island railroads have filed a joint application with the Interstate Commerce Commission seeking authority for Southern Pacific to buy almost 992 miles of the Rock Island line for $57 million.

The application follows approval of the proposed transaction by the United States District Court in Chicago which has jurisdiction over Rock Island's current reorganization.

If approved by the ICC, Southern Pacific would acquire Rock Island railroad properties and operating rights on a 965-mile stretch between Santa Rosa, New Mexico and St. Louis, via Kansas City, Mo. The line is part of the "Golden State Route" which has been operated by the Rock Island and Southern Pacific for more than 70 years.

The package would also include a 26.5 mile branch line between Bucklin and Dodge City, Kan.

SP said it has been trying to obtain the Golden State route for 15 years to strengthen what it called the "potentially most efficient rail route between Southern California and the Midwest." The acquisition would allow SP and its Cotton Belt subsidiary to provide single-system service over the route and connect directly at Kansas City with several additional midwestern rail lines, including the Rock Island.

Rehabilitation is needed for the route extending northeast from the present Southern Pacific-Rock Island connection in New Mexico, SP explained, but when completed, it would provide shippers with 400-mile shorter route for the substantial amount of traffic moving between the Pacific Coast and the St. Louis gateway. The rehabilitation program will cost about $224 million, according to the reports of consulting firms whose recommendations were appended to the application.

The purchase would give the SP rail system a total of 14,411 miles of railroad in 14 states.

The ICC has until Jan. 26 to decide whether to accept the application for consideration, and 14 months from the date of acceptance to decide whether to approve it.