26 March 1924
Blackouts led to loss of steering and propulsion on 984-foot-long vessel.
NTSB investigation
On 18 November the US NTSB said that a single loose wire on the 984-foot-long
containership Dali caused an electrical blackout that led to the giant vessel veering and
contacting the nearby Francis Scott Key Bridge in Baltimore, which then collapsed, killing six
highway workers.
A sequence of events
At a public meeting at NTSB headquarters investigators said the loose wire in the ship’s
electrical system caused a breaker to unexpectedly open – beginning a sequence of events
that led to two vessel blackouts and a loss of both propulsion and steering near the 2.37-
mile-long Key Bridge on 26 March 2024. Investigators found that wire-label banding
prevented the wire from being fully inserted into a terminal block spring-clamp gate, causing
an inadequate connection.
Loss of propulsion
After the initial blackout, the Dali’s heading began swinging to starboard toward Pier 17 of
the Key Bridge. Investigators found that the pilots and the bridge team attempted to change
the vessel’s trajectory, but the loss of propulsion so close to the bridge rendered their actions
ineffective. A substantial portion of the bridge subsequently collapsed into the river, and
portions of the pier, deck and truss spans collapsed onto the vessel’s bow and forwardmost
container bays.
A seven-person road maintenance crew and one inspector were on the bridge when the
vessel struck. Six of the highway workers died. The NTSB found that the quick actions of the
Dali pilots, shoreside dispatchers and the Maryland Transportation Authority to stop bridge
traffic prevented greater loss of life.
NTSB Chair’s comments
NTSB Chairwoman Jennifer Homendy commented:
‘Our investigators routinely accomplish the impossible, and this investigation is no different.’
‘The Dali, at almost 1,000 feet, is as long as the Eiffel Tower is high, with miles of wiring and
thousands of electrical connections. Finding this single wire was like hunting for a loose rivet
on the Eiffel Tower.’
‘But like all of the accidents we investigate, this was preventable. Implementing NTSB
recommendations in this investigation will prevent similar tragedies in the future.’
Lack of countermeasures
Contributing to the collapse of the Key Bridge and the loss of life was the lack of
countermeasures to reduce the bridge’s vulnerability to collapse due to impact by ocean-
going vessels, which have only grown larger since the Key Bridge’s opening in 1977. When
the Japan-flagged containership Blue Nagoya contacted the Key Bridge after losing
propulsion in 1980, the 390-foot-long vessel caused only minor damage. The Dali, however,
is ten times the size of the Blue Nagoya.
Vulnerability of bridges nationwide to potential collision
As part of the investigation, the NTSB in March released an initial report on the vulnerability
of bridges nationwide to large vessel strikes. The report found that the Maryland
Transportation Authority—and many other owners of bridges spanning navigable waterways
used by ocean-going vessels—were likely unaware of the potential risk that a vessel
collision could pose to their structures. This was despite longstanding guidance from the
American Association of State Highway and Transportation Officials recommending that
bridge owners perform these assessments.
The NTSB sent letters to thirty bridge owners identified in the report, urging them to evaluate
their bridges and, if needed, develop plans to reduce risks. All recipients have since
responded, and the status of each recommendation is available on the NTSB’s website.
New safety recommendations.
As a result of the investigation, the NTSB issued new safety recommendations to the US
Coast Guard; US Federal Highway Administration; the American Association of State
Highway and Transportation Officials; the Nippon Kaiji Kyokai (ClassNK); the American
National Standards Institute; the American National Standards Institute Accredited
Standards Committee on Safety in Construction and Demolitions Operations A10; HD
Hyundai Heavy Industries; Synergy Marine Pte. Ltd; and WAGO Corporation, the electrical
component manufacturer; and multiple bridge owners across the nation.
The NTSB report
In accordance with Federal rules and agreements, the National Transportation Safety
Board (NTSB) has overlapping jurisdiction with the Coast Guard in respect to
conducting safety investigations for major marine accidents.
In this case, the Coast Guard has convened a Marine Board of Investigation and is
investigating, however the NTSB was designated as the lead federal agency for the
marine casualty to determine the cause of the accident.
NTSB’s staff are currently making final revisions to the report. It is understood that the complete document will be released in the coming weeks.
blackout that led to the vessel veering and contacting the Francis Scott Key Bridge in
Baltimore.
their terminal blocks. (Source: NTSB)