The B&M's most traveled and well known passenger trains included the "Alouette", "Ambassador", "Cheshire", "Day White Mountains", "East Wind", "Green Mountain Flyer", "Gull", "Kennebec", "Minute Man", "Montrealer"/"Washingtonian", "Mountaineer", "Pine Tree", "Red Wing", and "State of Maine". However, the popularization of the automobile doomed B&M as a passenger carrier. After steady growth from 1901 to 1913, passenger rail ridership around Boston peaked in 1920 and began to decline due to competition from private automobiles and service cuts during World War I. In the mid-1920s, after several difficult years, the B&M discontinued service on some marginal lines and began using small self-propelled railcars on others. A second round of discontinuances occurred from 1931 to 1936 as the Great Depression reduced traffic. Ridership sharply increased during World War II; the B&M had a slower postwar decline than its contemporaries, though major frequency reductions occurred in 1949-50. The B&M began testing Budd Rail Diesel Cars (RDCs) in 1952; in 1954, the railroad decided to switch all commuter service to RDCs to cut costs. Discontinuances in the 1920s and 1930s primarily affected minor branches and rural intercity routes, but the 1950s saw the loss of more significant intercity routes. September 1952 saw the first cut to the four main intercity mainlines, as Eastern Route service was cut from Portland, Maine to Portsmouth, New Hampshire. (Portland continued to see service to Boston on the Western Route through Dover, New Hampshire.) The New York–Montreal "Green Mountain Flyer"/"Mount Royal", which had Boston sections running on the B&M via Bellows Falls, ended when the Rutland Railroad cut all passenger service in 1953. The northern section of the Boston–Wells River, Vermont route ended in 1954 (thus ending connections to Quebec City), as did Manchester–Portsmouth service. Concord–Claremont Junction service ended in 1955, and the Boston section of the "Ambassador" was reduced to a Boston–White River Junction RDC connecting train in 1956. Fitchburg mainline service was trimmed from Troy, New York to Williamstown, Massachusetts in January 1958. The B&M became unprofitable in 1958 and moved to shed its money-losing passenger operations. On May 18, 1958, the B&M severely reduced Boston commuter service.