All Aboard! Next Stop, Rivendell
If you ever wondered “What was Saruman thinking?” while reading Lord of the Rings, Towards a New Railway History of Middle-Earth explains all: He was planning to start up a steam-driven railway.
The Railway History continues and explains how the half-orcs of Isengard turned out to be the ideal people to build the Middle-Earth railway system.
It is a thing little remembered – even by the Wise – that Dwarven miners had been laying or carving tracks along the floor of their tunnels to ease the movement of ore trucks and other gear since at least the end of the Second Age. Moria, in its time of glory, was completely spanned by such, and a cable-hauled gravity-assisted rack-and-pinion railway was laid in the to take mithril and gems down to Lorien, and return with such provisions as even Dwarves need.
Saruman however was obsessed with efficiency and progress. In the ruins of Isengard, near the base of Orthanc, the men of Rohan came across a detailed scale model of the Ring of Isengard as it might become after victory, and rails ran everywhere, complete with little working steam engines, stations with tiny model Orcs waiting on the platforms – some with tinier Orc babies, it was never true that Orcs were born from vats though some of the larger ones may have been grown in them – and troop trains full of Uruk-Hai in complex and colourful uniforms correct in every detail, The Horse-Lords could make nothing of this, thinking it some complex charm, and the layout was not understood for what it was till it fell into the hands of one of Peregrine Took’s grandsons almost a century later.
On the other hand, what happened to Saruman after LOTR? He was a Maia and presumably had several spare bodies. Maybe he was the moving spirit behind the railway system. His earlier attempt to use a Ring of Power was a disaster, of course, similar to the current belief that only a Ring of Power (i.e., a government) can run mass transit.
As for his other post LOTR activities, nobody else knew about them until Fangorn Wood was leveled by a 50-megaton nuclear blast…