There used to be two routes from Zagreb to Split. The older, slower Lika line, which went through the mountains, and the Una line, which follows the Una river on the border with Bosnia until it meets the Lika line in Knin.
The Una line was completed soon after WW2 and was much more popular. It was fully electrified to Knin by the late 1980s. It suffered significant damage in the war, and even though it was repaired by the year 2000, it was never fully reactivated
https://blog.vladovince.com/traveling-the-una-railroad-thoughts-on-potential-revitalization/
