Mike B, on 29 January 2017 - 02:14 PM, said:
Pretty much everything other than electric and diesel MUs in the US and Canada had steam heat until the 1970s, so diesel and electric passenger locomotives needed steam generators (a small, packaged boiler with automatic controls) for train heating. HEP started appearing on some commuter trains in the 1960s, then VIA did it for their whole fleet, then Amtrak did when they started replacing the Heritage cars. Heritage cars were eventually rebuilt with HEP for Amtrak, as they were for Via, which eliminated the need for steam generators on the locomotives. So for passenger trains well into the 1970s or even early 1980s, with Heritage-type cars, a steam-heat effect would be realistic.
Trains were pre-heated in terminals from a boiler in the station before the locomotive coupled up and connected its steam heat line. So steam heat effects (small plumes) at key points around the platforms (typically near the bumper post for stub-end terminals) would also be appropriate.
Effects would include steam leakage from hose joints, valves, and other release points. One interesting use was for cooling (air conditioning) that could be done with a steam ejector. Effects would be outside-temperature sensitive (can we do that in OR?) with stronger effects when cold and practically vanishing in warm weather, but not particularly throttle-sensitive.
Perhaps adding all these details would consume too much memory especially if the train were fairly lengthy.