My Grandfather,Norman Patterson was an engine driver for the limited express steam locomotive between New Plymouth and Wellington dueing the 1940s-1950s.He and his wife Vera lived in a Railway house on Belt Rd,NP. I still have the black & white photo framed of him in his uniform standing beside his locomotive.
With steam locos most of what you see coming out is nothing more than super heated water ie steam, sometimes the driver and fireman if there a lot of people with cameras will put more coal on, to make more smoke, but a properly run steam loco can be very efficient and not blow excessive black smoke, with regards to the DA,s their diesel engines were designed nearly 70 years ago so they are not as efficient as later model diesel engines.
