Line 300 is one of Căile Ferate Române's main lines in Romania, having a total length of 647 km. The main line, connecting Bucharest with the Hungarian border near Oradea, passes through Ploiești, Brașov, Sighișoara, Teiuș, and Cluj-Napoca. The section between Bucharest and Ploiești is shared with CFR line 500. Line 300 makes up part of the TEN-T Rhine–Danube Corridor. In this context, the line is to be greatly upgraded, improving speed, capacity and interoperability (train lengths, ERTMS). The section between Câmpina and Predeal was upgraded between 2007 and 2011, bringing several improvements to the infrastructure along the route. Between 2012 and 2018, the Coșlariu–Sighișoara section was extensively upgraded to speeds of up to 160 km/h, including the construction of bridges and tunnels to straighten out the alignment of the railway.

Secondary lines