The Washington and Old Dominion Railroad switched from electric to diesel power during World War II. In 1941-42 the railroad bought its first three diesel-electric engines. Each General Electric engine had 380 horsepower and weighed 44 tons. Later engines weighing between 65 and 75 tons operated at about 660 horsepower. The railroad was phasing out passenger service in favor of more profitable freight hauling. Diesel power allowed the W&OD to participate in Northern Virginia’s growth boom in the 1940s and 50s. Trains hauled brick, lumber, and cement from Alexandria. Gravel was loaded into cars at Trap Rock Quarry and hauled eastward to be used as fill for roadbeds. As diesel engines got bigger, Goose Creek Bridge could not withstand their weight, so railroad cars were transferred to smaller engines for the trip across the bridge and westward. By the 1960s the encroachment of these same roads spelled the end of local suburban railroads, including the W&OD.