[1] Ferry crossings in the outer Oslofjord have been documented back to 1582 when the notes of Bishop Jens Nilssøn mention it was common to travel over the fjord, with Jeløya as the east quay.

In a letter dated 1712 King Frederick IV asked the magistrate in Borre to build a larger ferry able to hold 16 horses and 50 men.

In 1784, decisions on the ticket prices were set at 40 shillings in summer and 60 in winter for a ferryman to row a boat with twelve men across.

In 1884, Consul Richard Peterson started using the steamship Axel to cross the fjord, and a year later Bastø entered service, while Horten was bought as a reserve.

To get more capacity another Bastø II was delivered in 1939 from Moss Værft og Dokk, capable of holding 600 passengers and 34 cars.

On 9 April 1940, the ferry continued its ordinary traffic in the stream of German warships, which were coming into the fjord to occupy Norway.

Traffic increased steadily and in 1956 the next ship, named Bastø I was delivered with a capacity of 600 passengers and 55 cars.

Because of increased traffic and higher crew costs, the development went in the direction of larger ferries; Bastø V was delivered in 1973 with a capacity of 500 passengers and 120 cars.

In 1989, it was sold to Gokstad AS, the private company of the retiring Chief Executive Officer Bjørn Bettum.

An alternative includes also building a railway line parallel with the tunnel; this would make it 32 kilometres (20 mi) long to allow a gradient of 2.5%.

[5] Since 2014, the process became more concrete and the local debate louder after the Public Roads Administration published a concept evaluation study (KVU).