However, beyond this their design was largely similar - aside from the PA/PB's both being larger A1A-A1A types with an even more striking nose - and many railroads used FA and PA locomotives for both freight and passenger service.

Finally, the 1,800 hp (1,300 kW) FPA-4/FPB-4, powered by the 251 V-12 engine, was built between October 1958 and May 1959 by ALCO's Canadian subsidiary, Montreal Locomotive Works (MLW).

This unusually short testing sequence was brought about by the decision of ALCO's senior management that the engine and an associated line of road locomotives had to be introduced no later than the end of 1946.

Two FA-1s and an FB-1 were painted in ALCO Demonstrator colors and were released for road tests for a month and a half on the Delaware and Hudson Railway.

Before the end of this production run, ALCO upgraded the generators and traction motors in the locomotives, with the first of these models entering service in February 1947 for the New York Central.

The traction motors were removed, and original prime movers replaced with 600 horsepower (450 kW) engines/generators solely for supplying Head-end power (HEP).

By the late 1990s and early 2000s, the railroad began retiring the ALCOs in favor of new bi-level cab cars and locomotives with HEP installed.

ALCO and MLW built 152 of the various FP models with the largest quantity, 38% of the total production, sold to Canadian National Railway.

[4] Several excursion railways own operating examples which are in regular service, including MLW units received from Via Rail Canada.

Variants of the ALCO "World Locomotive" saw service in Australia, where it was built under license by AE Goodwin, Sydney.

A few months later, the first of an up-rated version of the two-cab design arrived on the Department of Railways New South Wales as the 44 class, of which 100 were in service by 1968.