The 2.2km long Chortanovci tunnel is designed as two single track tubes. This design is necessitated by the geology of the region. The tunnel is part of the high-speed railway Stara Pazova - Novi Sad, and in larger scale part of the Belgrade - Budapest line. The tunnel was built using the new Austrian NATM method.

details of the innovative methods are explained in Serbian here but also another publication provides detailed English translation:

https://tekdeeps.com/innovative-method-applied-on-demanding-terrain-chortanovci-tunnel/