Diesel locomotive
Diesel locomotives offer significant operating advantages over steam locomotives. They can safely be operated by one person, making them ideal for switching/shunting duties in yards (although for safety reasons many main-line diesel locomotives continue to have 2-man crews: an engineer and a conductor/switchman) and the operating environment is much more attractive, being quieter, fully weatherproof and without the dirt and heat that is an inevitable part of operating a steam locomotive. Diesel locomotives can be worked in multiple with a single crew controlling multiple locomotives in a single train — something not practical with steam locomotives. This brought greater efficiencies to the operator, as individual locomotives could be relatively low-powered for use as a single unit on light duties but marshaled together to provide the power needed on a heavy train. With steam traction a single very powerful and expensive locomotive was required for the heaviest trains or the operator resorted to double heading with multiple locomotives and crews, a method which was also expensive and brought with it its own operating difficulties.
Track pan
Diesel locomotives were introduced in the United Kingdom by British Railways in the 1950s, working alongside steam traction until 1968. Passenger vehicles were heated by steam from the locomotive boiler at that time, and the early diesel locomotives were provided with auxiliary boilers to provide the steam. Locomotives intended for long non-stop runs (such as the Class 40 and Class 55) were fitted with water scoops to allow them to replenish the steam generator's water supply from troughs/pans. The withdrawal of steam traction and the introduction of rolling stock with electric rather than steam heating removed the need for such equipment on later types and scoop-equipped locomotives had their scoops removed.