Another route that might fit your criteria is the *Traunseetram*, an 18.6 km line connecting the towns of Gmunden and Vorchdorf in Austria.

The equipment used would probably qualify as a tram rather than a train (although I'm by no means an expert), its tracks run on the street for the section in Gmunden, and along a road for the last few kilometres into Vorchdorf.
It also offers a nice view of the mountains and the entire route most certainly qualifies as rural:
[![enter image description here][1]][1]
[Image source][4]

For the most part, however, it does not run along a road like you specified.

You can find more information on the [operator's website][2] (German only), the (very short and uninformative) English [Wikipedia entry][3], or its more extensive [German version][5].


  [1]: https://i.sstatic.net/VkpQ4.jpg
  [2]: https://www.stern-verkehr.at/portfolio/traunseetram/
  [3]: https://en.wikipedia.org/wiki/Traunseebahn
  [4]: https://www.wander-spass.at/oesterreich-poi/detail/430001842/traunseetram-gmunden-bahnhof-vorchdorf-eggenberg.html
  [5]: https://de.wikipedia.org/wiki/Lokalbahn_Gmunden%E2%80%93Vorchdorf