HOUSTON — A recent report by the National Transportation Safety Board (NTSB), released Thursday has raised urgent concerns about the vulnerability of U.S. bridges to vessel strikes, highlighting potential risks in Houston and the surrounding region.
The report, titled Safeguarding Bridges from Vessel Strikes: Need for Vulnerability Assessment and Risk Reduction Strategies, identifies 68 bridges nationwide that may be at risk of collapse if struck by a vessel. Several of these structures—including the Sidney Sherman Bridge, Rainbow Bridge, Veterans Memorial Bridge, and Buffalo Bayou Toll Bridge—are located in Houston, Beaumont, and Port Arthur, where high vessel traffic and aging infrastructure create increased risks.
The report was commissioned after the March 2024 collapse of the Francis Scott Key Bridge that left six people dead.
Understanding the vulnerability assessment
The NTSB’s findings stemmed from a nationwide assessment of bridges over navigable waterways. The vulnerability assessment is a risk model that evaluates a bridge’s susceptibility to collapse in the event of a vessel collision. It takes into account:
- Bridge and span geometry
- Pier protection and lateral capacity
- Vessel traffic patterns and speeds
- Waterway characteristics
The assessment follows AASHTO’s Method II risk model, which calculates the annual frequency of collapse (AF). If a bridge exceeds AASHTO’s risk threshold, it is considered high risk.
The Baltimore Key Bridge collapse & its warning for Houston
The report was prompted by the March 26, 2024, disaster when the 984-foot containership Dali lost power and struck Pier 17 of the Francis Scott Key Bridge in Baltimore, Maryland. The impact caused a catastrophic collapse, killing six construction workers and injuring others.
Following the collapse, the NTSB conducted a post-incident vulnerability assessment. The results revealed that the Key Bridge had a calculated AF nearly 30 times greater than AASHTO’s risk threshold for essential bridges (0.0001).
The lack of modern protective systems, aging structural design, and increasing vessel sizes were key factors in the collapse.
Bridges in Houston
In the greater Houston region (within a 150-mile radius), the NTSB identified four major bridges as having unknown levels of risk due to aging infrastructure and heavy maritime traffic. These bridges have not undergone a vulnerability assessment based on modern vessel traffic patterns, raising concerns about their safety.
1. Sidney Sherman Bridge (I-610 Ship Channel Bridge)
- Year Built: 1973
- Classification: Critical/Essential
- Risk Factors: Proximity to the main navigation channel, high petrochemical shipping traffic, aging design, increasing vessel sizes, and limited room for off-course vessel correction.
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2. Rainbow Bridge (Port Arthur)
- Year Built: 1939
- Classification: Critical/Essential
- Risk Factors: Tallest bridge in Texas, frequent tanker and barge traffic from the Sabine-Neches Waterway, older structural components, and potential exposure to increased vessel impact forces.
3. Veterans Memorial Bridge (Port Arthur)
- Year Built: 1991
- Classification: Critical/Essential
- Risk Factors: Older design standards, significant oil and chemical tanker traffic servicing Gulf Coast refineries, lack of modern pier protection systems, and potential for vessel collisions due to narrow channel width.
4. Buffalo Bayou Toll Bridge (Harris County)
- Year Built: 1980
- Classification: Typical
- Risk Factors: High-volume barge traffic, aging structural components, limited vessel-collision protection measures, and increased vessel sizes over time.
These four bridges have not been assessed using AASHTO’s modern risk model, meaning their actual risk levels remain unknown.
What happens next?
The NTSB has issued urgent recommendations to the Texas Department of Transportation (TxDOT) and the Harris County Toll Road Authority, calling for immediate vulnerability assessments on these high-risk bridges.
If assessments determine that a bridge exceeds AASHTO’s risk threshold, owners must take corrective action, which may include:
- Installing additional protective structures (e.g., dolphins or fendering systems)
- Reinforcing bridge piers to withstand vessel strikes
- Implementing navigation controls to slow or redirect large ships near high-risk bridges
The NTSB is also urging federal agencies—including the U.S. Coast Guard, U.S. Army Corps of Engineers, and the Federal Highway Administration—to support state and local agencies in reducing vessel-strike risks.
Economic and safety implications
Beyond public safety concerns, a bridge collapse in Houston, Beaumont, or Port Arthur could have severe economic consequences.
According to the Greater Houston Port Bureau, the Houston Ship Channel alone contributes $802 billion to the U.S. economy annually. A bridge collapse in this corridor could:
- Halt port operations, disrupt supply chains, and delay critical energy shipments
- Cause massive traffic congestion in affected metro areas
- Increase costs for businesses relying on maritime transport
Call for action
As vessel sizes grow and shipping traffic intensifies, the risk of bridge collapses due to vessel strikes increases. The NTSB’s recommendations are part of a nationwide effort to enhance bridge safety, strengthen infrastructure resilience, and protect vital transportation corridors.