[4] The company Johannes Sørlie launched an all-tunnel proposal in 1985, estimated to cost 700 million Norwegian krone (NOK) and which would have resulted in 18 kilometers (11 mi) of subsea tunnel connecting Bømlo, Stord and the mainland.

[4] An inter-municipal committee was positive to the proposals, while Josef Martinsen, director of Hordaland Public Roads Administration, stated that the project was unrealistic.

[6] A report published by SBT in 1987 considered detailed plans for a subsea tunnel to the mainland, which was followed up by seismic surveys in the fjord.

SBT changed its name to Sunnhordland Bru- og Tunnelselskap, and a majority of the board shifted towards being in favor of a fixed link.

[7] The Norwegian Coastal Administration stated that they would not allow a pontoon bridge, as it would interfere with ship traffic.

[8] On 26 June 1987, SBT's board decided to work towards getting permission to collect advance tolls on the ferry services.

[10] This was criticized by Hordaland Public Roads Administration, who stated that it would take a longer time to plan, and thus complete, the Triangle Link.

[13] Also Gisle Tjong, a local citizen, opposed the project, stating that the risk was too large and that it was uncertain how long the tolls would last.

Instead, he wanted to use advance tolls and fuel fees, place the income in the bank and then pay the whole fixed link with the saved-up funds.

The exception was in southern Bømlø, where there was concerns that their ferry service to the mainland would be terminated, which would result in considerably longer driving time to Haugesund.

[15][16] Hordaland Public Roads Administration still supported a pontoon bridge, and stated that two and a half years of work on a master plan had been wasted.

[19] On 10 December 1992, Parliament approved advanced payment of tolls on the ferry, which were made effective from 1 January 1993.

It included safety and environmental improvements which increased the project's cost by NOK 200 million,[20] and it was made subject to consultative statements in May 1994.

[21] Following a dispute regarding the impact of the bridge landing on Stord, SBT proposed building a culvert on Digernes as a compromise to avoid developing a new plan which could have postponed the project several years.

[24] Late core samples showed that the tunnel would have to be located 30 meters (98 ft) further down than originally planned to avoid deposits.

[26] The Bømlafjord Tunnel is 7,860 meters (25,790 ft) long and crosses Bømlafjorden as part of European Route E39.

[27] Safety measures include fire extinguishers, emergency telephones and break-down pullovers every 250 meters (820 ft).

There are turning points for trucks every 1,500 meters (4,900 ft) and lights and barriers at the entrances to notify drivers if the tunnel is closed.

It features radio coverage and a system to register the position and key information about all vehicles in the tunnel.