Seaboard RS3 road-switchers By Angela Cotey | December 2, 2021 Email Newsletter Get the newest photos, videos, stories, and more from Trains.com brands. Sign-up for email today! Get Updates Two Seaboard Air Line RS3 road-switchers work at Madison, Fla., in 1965, two years before the road merged with the Atlantic Coast Line. Alco introduced the RS3 in 1950, producing some 1,370 of the 1,600 h.p. units. Harry L. Juday photo