As early as 1936, the Italians electrified the Pivka-Rijeka line (not part of the current M202 railway) at the standard 3 kV DC voltage.

As such, it became favoured in the 1950s and early 1960s, and electrification of the Zagreb-Rijeka line began: However, in the later half of the 1960s, the Yugoslav Railways considered the 25 kV AC at 50 Hz system instead, which later became the national standard (the project was initially experimented in Bosnia and Herzegovina between 1967 and 1969).

In the first half of the 1980s, the Yugoslav Railways considered the full conversion of the remaining 3 kV DC network (by then present in all of Slovenia and parts of West Croatia) into the national standard.

Along the years, various proposals for the conversion of the network were done, including conversion of the Class 1061 locomotives to Class 1161 locomotives (these were 1061s with 25 kV AC systems, rebuilt at TŽV Janko Gredelj) but eventually, the plans didn't really materialize, as Slovenia insisted on keeping the 3 kV DC electrification, and lack of funds in early 1990s Yugoslavia and Croatia led to the 1161 project to be abandoned.

Finally, in December 2012, the rest of the line, from Moravice to Rijeka (and further onwards to the border with Slovenia) was fully converted to 25 kV AC.