Inspection locomotive

An inspection locomotive was a special type of steam locomotive designed to carry railroad officials on inspection tours of the railroad property.
Background.
These were fitted with passenger car-like bodywork and seating. Many railroads in the nineteenth century owned one, but their use dwindled in the twentieth century. They were replaced with converted passenger-car inspection cars, or HiRail trucks, automobiles fitted with steel flanged wheels.
Some were especially built for this service, while others were rebuilt from obsolete locomotives. Many were quite small; the locomotive pictured is in fact one of the largest and most modern inspection locomotives ever constructed. They were generally well cared for and highly decorated.
Region specific.
Russia.
The Russian Railways still has two inspection locomotives A Chs2 549 & 552, which are converted electric locomotives.
United Kingdom.
Railway companies in the United Kingdom did not use inspection locomotives. Instead dedicated carriages (known as Inspection Saloons) were used. These were either rebuilt from obsolete coaching stock or, occasionally, were newly built. However many companies maintained dedicated locomotives to haul Inspection Saloons. These were usually elderly engines that had been famous top-rank express locomotives when new but had since been surpassed. Examples of such engines include the Caledonian Railway Single, LNWR No.3020 'Cornwall' and NER No. 66 'Aerolite'. Dugald Drummond, when Chief Mechanical Engineer of the London and South Western Railway had a small 4–2–4 tank locomotive with a small saloon body mounted on its rear to serve as his personal transport around the L&SWR system on inspections and visits.
United States.
The only known surviving U.S. example is the Reading Railroad's "Black Diamond", a tiny 2-2-2 with fully enclosed bodywork, at the Museum of Transportation in St. Louis, Missouri.