Minnesota Department of Transportation
I-35W Mississippi River Bridge Collapse
Estimated impact: $400M replacement cost; 13 deaths; 145 injuries
The I-35W bridge in Minneapolis collapsed during rush hour, killing 13 people and injuring 145. The bridge had been rated "structurally deficient" since 1990, and a 2006 inspection found cracked gusset plates. MnDOT chose ongoing monitoring rather than load restrictions or replacement.
Decision context
Whether to impose load restrictions, close, or replace the I-35W bridge after repeated inspections identified structural deficiencies and undersized gusset plates.
Decision anatomy
Red = risk factor present · Green = protective factor present
Biases present in the decision
★ Primary driver · Severity estimated from bias type and decision outcome
Toxic combinations
Reference class base rates
Across all 143 curated case studies in our library:
Lessons learned
- Status quo bias in infrastructure: bridges rated "structurally deficient" continue operating because closure has immediate visible costs while collapse is probabilistic
- Anchoring to the bridge's 40+ years of service created false confidence that it would continue to perform despite declining condition
- Cognitive misering: inspections identified problems but the response was monitoring rather than action — observing risk is not the same as managing it
Source: NTSB Highway Accident Report HAR-08/03 (2008) (NTSB Report)
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