The National Transportation Safety Board (NTSB) has determined that the collapse of Baltimore's Francis Scott Key Bridge in March 2024, which resulted in the deaths of six highway workers, was caused by a wrongly installed wire label. This installation issue led to electrical problems on the containership Dali as it approached the bridge.
The NTSB's final report, released this week after a board meeting in November, clearly identifies the accident's main cause. Investigators noted, “the probable cause of the contact between the containership Dali and the Francis Scott Key Bridge was a loss of electrical power (blackout), due to a loose signal wire connection to a terminal block stemming from the improper installation of wire-label banding, leading to the vessel's loss of propulsion and steering near the bridge.”
The 984-foot Dali, registered in Singapore, collided with Pier 17, the southern support for the central part of the bridge, around 1:29 a.m. on March 26, 2024, after losing all electrical power, propulsion, and steering. The collision caused a significant section of the bridge to fall onto the ship's bow and front cargo areas.
The damage to the Dali is estimated at over $18 million, while replacing the bridge is projected to cost between $4.3 billion and $5.2 billion, with the new bridge not expected to open until late 2030. Tragically, six out of seven members of a road maintenance crew lost their lives in the collapse, leaving one worker seriously injured and an inspector unharmed.
The NTSB reported that “the crew’s inability to regain propulsion after losing electrical power was partly due to the limited time they had since the Dali was very close to the bridge.” Investigators also pointed out weaknesses in infrastructure protection, stating that “the absence of measures to reduce the bridge's vulnerability to impacts from large vessels contributed to the collapse, which could have been addressed if the Maryland Transportation Authority had conducted a vulnerability assessment.”
Failures in communication worsened the situation. The NTSB found that “the lack of effective and immediate communications to warn the highway workers to evacuate the bridge also contributed to the fatalities.”
In response to this incident, the NTSB has made several safety recommendations, including four marked as urgent. They have urged the Federal Highway Administration, U.S. Coast Guard, and Army Corps of Engineers to form a team to help bridge owners assess and minimize the risk of vessel collisions. More than two dozen state transportation departments and bridge authorities have been instructed to evaluate collapse risks for vulnerable bridges and create risk reduction plans if these evaluations indicate safety concerns.
The recommendations also cover broader issues. The Coast Guard has been asked to explore redundant propulsion systems for large single-engine cargo ships in restricted waters and to suggest changes to international safety management standards. Additionally, the NTSB wants enhanced standards for voyage data recorders, including capturing communications and data during blackout situations.
For the vessel operator Synergy Marine, the NTSB recommended implementing infrared thermal imaging to spot faulty electrical connections and ensuring that emergency systems are correctly configured to prevent automatic shutdowns during critical operations.
The bridge collapse has led to over 34,000 vehicles daily—10 percent of which are trucks and all hazardous materials carriers barred from using Baltimore's tunnels—diverting onto longer alternate routes, which has caused significant economic disruptions for the Port of Baltimore and the surrounding area.
This event serves as a powerful reminder of how minor mechanical failures can lead to catastrophic outcomes when critical infrastructure is not adequately protected and emergency response protocols are insufficient.
The final report is available on the NTSB's website.