The line is exclusively used for passenger trains, which are provided by Vy, which connect northwards to Oslo and south-westwards to Grenland.

The 13-kilometer (8.1 mi) section from Eidanger to Skien is often colloquially included in the Vestfold Line.The standard gauge line is electrified at 15 kV  16.7 Hz AC and has twelve remaining stations.

The entire line is electrified, has partial automatic train control and GSM-R.[1] It has 111 level crossings, of which 29 have light and bar.

[1] The route roughly follows the coastline of Oslofjorden whilst, concerning the first section, running from Drammen to Sande inland, bypassing thereby Oslofjords western finger Drammensfjorden.

Holmestrandsporten tunnel between Holm i Sande and Nykirke (Horten) was opened in 2016 as part of a double-track high-speed upgrading.

Due to practical reasons (avoidance of a terminus), Tønsberg once got a big loop downtown without horseshoe curve function.

In 2018, the original single-track route between Farriselva (Larvik) at lake Farris and Porsgrunn (via Oklungen) was abandoned in favour of a newbuilt double-track high-speed bypass, using several tunnels and not-so-small bridges.

[1] Public opinion started debating the need for a railway through Vestfold in the late 1860s, when the Randsfjorden Line was built to Drammen, opening in 1868.

There was also at the time problems with the inner parts of the Oslofjord and the Drammensfjord icing during winter, and access to the ports on the outer fjord would ease the export situation for industry.

[10] This alternative allowed the line to run through an area with good access to lumber, which the railway would aid export.

The outer followed the shore of the Oslofjord, would be 111 kilometers (69 mi) and would run through Holmestrand, Horten and Åsgårdstrand before reaching Tønsberg.

[13] A third major alternative was to bypass the coast altogether and build a connection from the Kongsberg Line at Skollenborg Station down the valley of Lågendalen to Larvik.

Pihl estimated the 45-kilometer (28 mi) extension to cost NOK 4.5 million, in addition to a possible branch to Brevik.

The first stated that the right-of-way should be built in preparation for conversion to standard gauge,[21] the latter was an attempt to stall construction and instead place the route through the interior.

The navvies were uncomfortable building a cutting south of Holmestrand, where the line went through an old cemetery in clay ground and they would often find well-preserved corpses while digging.

During construction of a level crossing at Smørstein on 17 August 1918 the area around the track started experiencing a series of landslides.

A propaganda committee was established in 1931, which in addition to gauge conversion insisted on that the line be rebuilt so it run via Horten.

[31] Vy introduced its new InterCityExpress concept, which resulted in an increase of patronage by twenty-five percent on the Vestfold Line.

[30] The first stages of modernization of the Vestfold Line were carried out through a combination of new trains and sections of double track.

[47] Despite the upgrades, by 1997 the trains from Larvik to Oslo were using twenty minutes longer than they were in 1973, and the average speed on the Vestfold Line was down to 65 km/h (40 mph).

[50] In September 1999, the government presented their proposal for National Transport Plan 2002–11, which included three segments on the Vestfold Line: Holm–Nykirke, Barkåker–Tønsberg and Farriseidet–Porsgrunn.

[56] In response, Minister of Transport Torild Skogsholm stated that she was considering financing the project as a public–private partnership paid through a surcharge on tickets fares.

[58] The go-ahead for the 7.7-kilometer (4.8 mi) Barkåker–Tønsberg section, including the Jarlsberg Tunnel, was given by Minister of Transport Liv Signe Navarsete on 31 March 2008, estimated to cost 1.37 billion Norwegian krone (NOK).

[60] The short segment gives little operational advantages,[60] while hindering a new line from running via the population centers of Horten, Åsgårdstrand and Eik.

Balthazar Lange was selected as the line's main architect, although some minor buildings were standardized designs by Peter Andreas Blix.

The stations were innovative for their design with a central vestibule with direct access to both the town and track sides, with branches to waiting rooms for second and third class.

Plans call for an initial construction of the Inner Intercity Triangle, which will give continual double track from Tønsberg to Oslo, in addition to the shortening of the segment between Larvik and Porsgrunn.

The line could accommodate an estimated 9.5 million passengers per year, and each station could receive between 100 and 500 percent increase in patronage.

Designed for speeds of 250 km/h (160 mph), the new segment will feature the 12.3-kilometer (7.6 mi) Holmestrandfjellet Tunnel, which will contain the four-track Holmestrand Station.

One alternative was a suspension bridge across Drøbaksundet, which could be built to accommodate trains and feature a main span of 1,300 and 1,500 meters (4,300 and 4,900 ft).