The Jarlsberg Tunnel constitutes the southernmost part of the double-track segment of the Vestfold Line between Barkåker and Tønsberg. It is electrified at 15 kV 16.7 Hz AC, has an NSI-63 signaling system and is dimensioned for . The crosscut serves as an emergency exit. The railway tunnel crosses above the Frodeåsen Tunnel, a twin-tube tunnel of County Road 300. The tunnel's single crosscut serves as an emergency exit. The line is owned and maintained by the Norwegian National Rail Administration.