“The Yara Birkeland project and the Asko barge project are pushing the technology out into the real world, and not just in research labs, like we have been doing for many years.”

When it comes to safety, crewless vessels need to perform as well, if not better than captained ships says Prof Tannum, who believes there will always needs to be a backstop – someone monitoring who could intervene if necessary.

“Since this is very new technology and not tested in real life that much, we need this transitional period with crew on board,” Prof Tannum says. “Then gradually, we can trust the autonomy to do more.”

Autonomy opens up possibilities for new designs though, he adds. “Without crew you can have more capacity for goods, because you don’t need the living quarters, galley, heating, air conditioning and other systems,” Prof Tannum adds.

There’s scepticism whether large unmanned ships could be crossing oceans any time soon, though. “First the legal challenges must be resolved. And then the ships needs robust energy and propulsion systems that require very little maintenance,” points out Prof Tannum.

One of the biggest hurdle is regulation and new rules will have to be drawn up.

“Current legislation has been developed based on the presumption that the equipment onboard a ship is fully manually controlled,” says Sinikka Hartonen, adding that the International Maritime Organization is now working towards a framework.

“The regulation is totally new territory for the marine authorities and politicians in Norway. What they do will have consequences internationally,” says Yara project manager Jon Sletten.

Whatever happens, progress in autonomous shipping is likely to move more quickly than autonomous cars and trucks, according to Prof Tannum.

“Autonomous cars move in high-speed close to both dynamic and static obstacles, road conditions vary and the complexity that cars in regular traffic faces is more challenging than ships.

“Unmanned autonomous ships with a fixed route and a remote operation center (ROC) will be operating with less risk than unmanned autonomous trucks driving in regular traffic,” he says.