Model types of General Motors were usually F for freight and E for passenger The E unit above has a steam generator to heat the railroad cars, still common until the 1990's as Amtrak still used passenger cars from pre 1971 until about then. The 2 major makers of diesels were GM Electro Motive and Alco. Alco called their units FA and FB (cabless booster) for freight, and PA and PB for passenger. What is called a B unit has no cab, and is controlled by the lead unit with a cab. The GM second generation of freight diesels were GP( 4 wheel trucks) and SD( 6 wheel trucks) General Electric came into the fray as Alco and a lot of smaller makers were leaving the industry, and GM and GE now battle for supremacy. Most locomotive cabs are now wide cabs here, as we no longer have cabooses since the 1980s, and there are only 2 man crews instead of the 4 man crews of yore.
