Dennis William Brosnan Jr., 82, a former president and chairman of the Southern Railway who believed that the way to run a railroad was to get out and run it, died of cancer June 14 at his home in Asheville, N.C.

Mr. Brosnan joined the Southern in 1926 as a student apprentice laying track. He was president from 1962 to 1967 and then spent about a year as chairman. He was a director of the Norfolk Southern, the railroad's parent company, until 1983.

His career was on the operating side of the business rather than in finance or other phases of it, and he was credited with bringing about major improvements through centralization, automation, rail welding, centralized wheel and axle maintenance, and other innovations.

He believed not only that "The Southern Serves the South," as it says in its motto, but also that it should grow and prosper as the region grows and prospers. And he meant to see that it did. To this end he forsook the Southern's headquarters at 15th and K streets NW for two executive passenger cars and a company airplane, and in these he checked up on just about everything there was to see up and down almost 11,000 miles of track. He maintained a residence in Washington from 1952 to 1967, but in one typical year he spent only 60 nights at home.

"I have never been what is called a white-collar executive," he once said. "I don't like the word executive. My desk is not a very clean one. I like to know what is going on and see it. I poke my nose in everything from privies to the IBM computers on our line."

Mr. Brosnan also was an astute salesman at a time when trucking was gaining on the railroads' traditional role as the nation's primary freight carriers and he sought ways to cut costs to make his line more competitive. An example of his salesmanship was his approach to getting a share of the North Carolina furniture manufacturing market. He found that the industry favored trucks because its wares often were damaged on freight cars. To fix this, he had special cars designed for furniture. To get a bigger share of the grain trade, which was growing in the South as its livestock and poultry industries flourished, he ordered 500 "Big John" grain cars, each of which was capable of carrying more than 100 tons, twice the capacity of earlier grain cars.

To the discomfiture of much of the railroad industry, he was known to forego rate increases authorized by the Interstate Commerce Commission. And in connection with the grain trade he pressed a lawsuit in which the U.S. Supreme Court eventually overturned the ICC's power to set minimum freight rates even when it thought lower rates would hurt other carriers. Mr. Brosnan contended that the regulations dated from a bygone era and that they made railroads uncompetitive.

Mr. Brosnan also made extensive use of computers for such tasks as keeping tabs on the location of all Southern freight cars, a move which by itself was said to have effected savings of $8 million a year. He installed electronic devices that automatically detected hot boxes. When he became president, the Southern was planning to buy 300 new diesels at a cost of $160,000 each. He found ways to do the same amount of work with only 84 diesels, thus saving the cost of more than 200 of the behemoths.

"Bill" Brosnan was born in Albany, Ga., where his father was a fireman and a farmer. He graduated from the Georgia Institute of Technology in 1923 with a degree in civil engineering. He spent three years working for the Georgia Highway Department before joining the Southern. It is said that he moved 25 times in 25 years. In 1952, however, he was named vice president for operations. In 1960, he was promoted to executive vice president and in 1960 to president.

In retirement, he lived in Asheville. He was a director of numerous companies, including the Florida East Coast Railway, the Richmond, Fredericksburg and Potomac Railroad, and the American Security and Trust Co. He also was a director of the Southern States Industrial Council, the Boys Clubs of America, the Committee of Economic Development and the National Safety Council.

He was a member of the Chevy Chase Club, the Metropolitan Club and the 1925 F Street Club. His hobbies included fishing and hunting -- the Southern's hunting and forest preserve in South Carolina is named in his honor.

Mr. Brosnan's wife, the former Louise Geeslin, died in 1973. Survivors include a son, Dr. D. W. Brosnan III of Asheville; a sister, Sally Thorpe Brosnan of Atlanta; a brother, J. Raymond Brosnan of Cape Coral, Fla., and four grandchildren.