Editing EMD F-unit (section)

==Passenger service==
[[File:Amtrak San Francisco Zephyr.jpg|thumb|right|300px|[[Amtrak]] No.&nbsp;113, an [[EMD FP7]], leading two [[EMD SDP40F]]s with the ''[[San Francisco Zephyr]]'' at the Yuba Gap in 1975]]
While the F-unit series was originally conceived for freight service, many were used to haul [[passenger train]]s. The original EMC FT demonstrator was equipped with a [[Steam generator (railroad)|steam generator]] in the B units for train heating. Several railroads took advantage of the large space in the rear of their [[B unit]]s to add steam generators. The first FTs built strictly as a passenger unit was the Santa Fe 167 four unit set in February 1945. Learning from that, EMD offered an optional steam generator on all later F unit models. It was mounted at the rear of the car body; steam-generator equipped locomotives can be recognized by the exhaust stack and safety valves protruding at the rear of the roof.

The F-units were popular passenger locomotives on mountain grades (where they were recommended by EMD), because a four-unit set had more motored axles than a trio of [[EMD E unit|E-units]] of equivalent power (16 versus 12) and thus had less chance of overloading the traction motors. Additionally, the four F-unit set had all its weight on driven wheels and was thereby capable of greater [[tractive effort]]. The AT&SF ''[[Super Chief]]'', [[Chicago, Burlington and Quincy Railroad|CB&Q]]/[[Denver and Rio Grande Western Railroad|D&RGW]]/[[Western Pacific Railroad|WP]] ''[[California Zephyr]]'', and [[Great Northern Railway (U.S.)|GN]] ''[[Empire Builder]]'' all used F units on their Chicago-West Coast routes in the 1950s. The F7 was also popular for commuter lines and other passenger service where the trains were short.