North Sea collision: What tech was onboard the two ships and why didn't it prevent a crash?

As investigators continue to evaluate why two vessels collided in the North Sea, experts believe there are more questions than answers about what technologies were working at the time. 

The Stena Immaculate, a US-charted oil tanker, was struck by the Solong, a container ship, off the coast of Yorkshire in the UK around 11 am CET on Monday morning. 

The Solong’s master was arrested on Tuesday on suspicion of gross negligence manslaughter. 

A statement from the Marine Accident Investigation Branch (MAIB) on Thursday said their investigation into the collision includes gathering information on "the navigational practices on board both vessels," fatigue management, the condition of the vessels, and the conditions at the time of the collision. 

So, what went wrong? What technologies should be on board both ships and could they have potentially malfunctioned?

Ship tracking technology can 'just be switched off'

The first layer of defence against maritime collisions is a ship’s automatic identification system (AIS), a short-range coastal tracking system that helps ships see each other more clearly in all conditions. 

The AIS system, originally designed to avoid collisions, continuously transmits the vessel’s identity, position, speed, and course to all other AIS-equipped vessels that are in an average range of 40 nautical miles (74 km). 

Since the early 2000s, the International Marine Organisation (IMO) mandates that commercial ships with over 300 gross tonnage and all passenger ships must have AIS technology on board. 

Guidelines from the IMO say that all ships, whether travelling or anchored in a specific position, need to keep their AIS systems on. 

However, marine surveyor William Caselton told Euronews Next that’s not always the case. 

"You can just turn it off," he said. "Vessels that wish to be covert can switch it off and not be seen". 

The only way that the public would know whether the AIS system was on at the time of the collision is if investigators decide to publicly release that information. 

So far, Caselton said authorities haven’t come forward to say that either vessel complied with AIS requirements. 

What other technologies prevent these collisions?

AIS works alongside radar technology on these types of ships, Caselton said, which sends out high-speed electromagnetic waves to establish the location, distance, velocity, and direction that it is going in. 

There are different IMO radar requirements based on the internal volume of a particular ship. 

The IMO’s Convention on the International Regulations for Preventing Collisions at Sea says that any vessels on the radar system at risk of collision need to “take avoiding action”. 

Other vessels nearby, if they see a potential collision, could also let out a “fog signal” alerting the ships to reduce speed to a minimum. 

It’s easier for authorities to "differentiate" between vessels more easily when radar and AIS are used together, according to NATO. The AIS data is automatically processed and can create "normalised activity patterns" for vessels which, if breached, will set off an alert. 

It’s not clear whether either vessel had the necessary radar technology broadcasting at the time of the collision, Caselton said. 

Even if all else failed, Caselton said captains still have their own sight to fall back on. 

The lights of a ship must be turned on, which would give them the respective captains at least three nautical miles (5.5 km) of visibility so that they can be seen even in tough weather conditions with low visibility, he said. 

At that point, Caselton said either captain could have used Channel 16 VHF, the international calling and distress radio channel, to communicate with each other about the impending collision. 

But, Caselton said authorities have not said whether either ship was in contact with the other, something he believes is "quite extraordinary". 

"So the captain could call [the vessel] by name and say you’re going to collide with us, you must take avoiding action now," he said. "If you’re driving on the road, you honk at them to get out of the way - it's the same sort of thing with these technical devices".