Could tugboats have prevented the Baltimore bridge collapse? They would have helped, experts say
'With tugboats attached, you have immediate power available to modify the movement of a vessel'
As the focus in the Baltimore bridge collapse shifts from a rescue operation to an investigation of why it happened, some maritime experts have questioned why the ship didn't have tugboat guides with it right before impact — and if they could have made a difference.
Early Tuesday morning, two tugboats owned by McAllister Towing helped the container ship Dali out of the dock, according to marine shipping data analyzed by the Baltimore Banner. They then left the cargo ship around 1:09 a.m., the newspaper reported. At 1:25 a.m., the ship began veering right.
The ship slammed into the pillar of the Francis Scott Key Bridge after losing power around 1:30 a.m. Tuesday. This caused a long span of the bridge, a major link in the region's transport networks, to crumple into the Patapsco River.
"The obvious answer is yes, they could have helped," Trevor Heaver, professor emeritus of transport operations and logistics at the University of British Columbia, told CBC News.
"With tugboats attached, you have immediate power available to modify the movement of a vessel."
In Vancouver, any loaded tanker moving under the Ironworkers Memorial Bridge is assisted by tugboats, according to the Vancouver Fraser Port Authority.
That said, it's not really possible to say if tugboats could have stopped the accident in Baltimore if they'd still been attached to the vessel, Heaver added, because there were a number of factors at play, including the speed of the container ship, how far the ship was from the bridge when it lost power, and the size and power of the tugboats.
"They obviously would have helped. How much they would have helped, we have no idea."
At least eight people fell into the water as the bridge collapsed. Two were rescued, but the other six, part of a construction crew that had been filling potholes on the bridge, were missing and presumed dead. A search for their bodies was underway Wednesday morning, according to Maryland State Police spokesperson Elena Russo.
In a statement to CBC News, a spokesperson for McAllister Towing said all its crew are "well and accounted for," and its foremost concern is for the victims.
The role of tugboats
Tugboats are used to tow and push larger vessels, and one of their primary tasks is to "assist with the berthing and unberthing of ships, particularly in ports with challenging navigational conditions," according to the Marine Safety Consultants website.
The Dali probably left the tugboats after departure in order to gain speed, Capt. Alain Arsenault, the executive director with the National Centre of Expertise on Maritime Pilotage, told CBC News Network.
He said in some parts of the world, ships have what are called "tethering tugs" that go in front of the ship "and can help if something happens."
"But we don't have that many of that in the U.S."
The port in Halifax has a number of safety mechanisms in place to avoid a similar tragic situation, harbour master Capt. Adam Parsons told Metro Morning. That includes a requirement that any vessel over a specific length has one or two tugs tethered to it, Parsons said.
"So that if you have a situation or one of these incidents, the tug vessels can bring the ship to safety."
Even with a fully loaded and massive container ship, like the Dali, tugboats could "absolutely" stop it from drifting.
"The theory is, and the concept is, that the tugs can assist and stop the vessel depending on its location."
'There are few things scarier'
Federal and state officials have said the crash appeared to be an accident. Capt. Michael Burns Jr. of the Maritime Center for Responsible Energy said bringing a ship into or out of ports in restricted waters with limited room to manoeuvre is "one of the most technically challenging and demanding things that we do."
There are "few things that are scarier than a loss of power in restricted waters," he said. And when a ship loses propulsion and steering, "then it's really at the mercy of the wind and the current."
When a ship loses propulsion power, it loses its ability to manoeuvre itself, Jin Wang, a professor of marine technology at Liverpool John Moores University, said on the Science Media Centre website.
"To avoid the shipping drift randomly to lead to possible collisions with other objects, the best way of mitigating possible consequences is to anchor the ship and also to ask emergency response and rescue services (e.g., tugs or similar ships) to assist the ship," Wang wrote.
Tom Sharpe, a former Royal Navy officer, wrote in the Telegraph that given the speed of the Dali, a tug forward would have struggled to have any "lateral effect" on the collision course. But a tugboat at the aft, or rear of the ship, may have made a difference.
"There is no reason (other than time and money) why [the ship] couldn't have had a tug attached aft or at least had one close by. This would have given the ship so many more options."
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With files from The Associated Press