Montreal Locomotive Works (MLW) M420

The Montreal Locomotive Works (MLW) M420 is a 2,000 horsepower, four axle road switcher locomotive, purchased by Canadian National, BC Rail, and Providence & Worcester. The locomotive remains in service today on various short-line railroads throughout North America.

Canadian railroads, CN specifically, are known for one of the most important safety and cosmetic contributions to North American locomotive design. The wide cab has become the standard of the industry in North America, as nearly every new locomotive is manufactured with a safety cab. Since the safety cab’s inception, various additional crew comforts and structural elements have advanced, and become a place where the crew could feel safe and secure at all times. However, it is important to reflect on the locomotive that brought the safety cab to fruition, the MLW M420.

Roger Puta


During the early seventies, the safety and security of the train crews was brought to the railroad’s attention by various unions. This led to the cooperation between train crews and locomotive manufacturers on how to improve the safety and comfort of the locomotive cab. This came in the form of the safety cab, which became standard throughout North America by the early nineties.

One of the first of many locomotive built to this specification was the M420, which was the competitor to GMD’s new GP38-2W locomotive. This effort was spearheaded by the head of Canadian National’s mechanical department, Bill Draper, who is also known for the “draper taper” on many full-cowl body locomotives.

Throughout production between 1973-1977, 90 A units and 8 B units were manufactured, with 80 being purchased by CN, 16 by British Columbia Railway (BC Rail), 2 purchased by Ferrocarriles del Estado,  5 for the Providence & Worcester, 2 for Roberval & Saguenay, and 15 for Ferrocarrill del Pacifico.

The CN variants of the locomotive were delivered in three batches. The first batch, delivered in 1973 was designated as MR-20a (2500-2529), the second, MR-20b (2530-2559), and finally, MR-20c (2560-2579). These units spent the majority of their operating life in the eastern portion of Canada. The BC Rail units were unique, as they included the railway’s signature style of two sets of ditch lights. BC Rail ordered 8 A-units, and 8 B-units, ordering sixteen in total.

Roger Puta

The Providence and Worcester M420s were unique, as they were constructed with ALCO FA trucks, per the railroad’s specifications. Two Mexican railroads ordered the locomotive, with Ferrocarriles del Estado ordering a special switching version of the locomotive, designated the M420TR. Several additional variations of the locomotive have been manufactured, including the M424, which was equipped with dynamic braking capability.

The M420s faithfully served the CN, BC Rail, and other roads for many years, as the CN variants were retired in 1998. These locomotives have found homes on various short-lines and regional carriers throughout North America, including Omnitrax, the St. Lawrence and Atlantic Railroad, Great Western Railway, Genesee Valley Transportation, operating in northeast Pennsylvania, and the Southern Railroad Company of New Jersey (SRNJ).


The MLW M420 locomotive is powered by a 2,000 horsepower, four-stroke, twelve cylinder, ALCO 251C prime mover, delivering power to four GE 752 traction motors. The locomotive has a starting tractive effort of 60,400 lbs, and a continuous tractive effort of 35,000 lbs. The units ride on MLW Zero Weight-Transfer (ZWT) trucks, and encompasses a top speed of 67 mph (108 kp/h).

Date Built1973-1977
Number Produced103
RailroadsCN (90)
BC Rail (16)
P&W (5)
Ferrocarriles del Estado (2)
Roberval & Saguenay (2) (M420TR)
Ferrocarril del Pacifico (15) (M420TR)
Max Speed67 mph (108 kp/h)
Prime MoverALCO 251C
Horsepower2,000 hp
Main GeneratorGE GTA17
Traction MotorsFour GE 752
Weight272,000 lbs
Length61 ft
Width10 ft 3 in
Height15 ft 6 in

Additional technical information available at The Diesel Shop.

Roger Puta



Lifelong Rail Enthusiast and Owner of Worldwide Rails

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