Louisiana Bridge Conditions
Louisiana has 13K bridges in the FHWA National Bridge Inventory. 3.9K (31%) are structurally deficient. Average bridge age is 44 years with an average Condition Score of 53/100.
Louisiana has one of the more challenging bridge-condition profiles in the FHWA dataset. 3,931 of 12,684 bridges are structurally deficient — 31.0 percent of the state inventory, well above the U.S. average. Average bridge age is 44 years.
For travelers and freight operators, the per-state aggregate is the macro picture; the per-bridge detail pages on this site surface the specific structures along any given route. Structurally deficient does not mean unsafe — FHWA explicitly notes such bridges remain open and safe when they meet load-rating requirements — but it does flag structures the owning agency has identified for rehabilitation or replacement.
Louisiana in the National Picture
Every figure on this page comes from the FHWA National Bridge Inventory, the federal database that aggregates state DOT inspection records under the National Bridge Inspection Standards. The NBI covers every public-road bridge longer than 20 feet in the United States and is the authoritative source for U.S. bridge condition data. State-level numbers are the sum of individual structure ratings; they reflect inspection records, not engineering judgments about overall network safety.
Louisiana's 31% deficient share is materially above the national average, with 3.9K bridges flagged. Higher percentages typically appear in states with older infrastructure, harsher climates, or both. The classification is descriptive of physical condition; it does not by itself indicate that a bridge is unsafe at posted loads, only that its rating triggers federal eligibility for replacement and rehabilitation funding.
Louisiana's average bridge age of 44 years is close to the national norm. Many U.S. bridges were built during the Interstate Highway System buildout in the 1950s through 1970s, which means a large share of the inventory is now in its design-life window where rehabilitation, deck overlays, and beam replacements become routine.
For an alternative national-level view, the ASCE Infrastructure Report Card publishes a single letter grade for U.S. bridges every four years drawn from the same NBI data, plus narrative analysis from civil engineers. ASCE's most recent assessment provides useful context for the per-state numbers shown here.
Worst Condition Bridges in Louisiana
The 20 bridges in Louisiana with the lowest BridgeWatch Condition Scores. A low score reflects poor NBI ratings on the deck, superstructure, or substructure — not a prediction of failure. Bridges remain open at posted load limits while their ratings are addressed by the state DOT through repair, rehabilitation, or replacement.
Highest Traffic Bridges in Louisiana
Average daily traffic counts from the NBI. Heavily-loaded structures carry disproportionate cumulative wear and are typically the highest-priority candidates when state DOTs allocate rehabilitation funding. Daily traffic figures can be a year or two behind current operational counts because they are reported on the NBI inspection cycle.
Frequently Asked Questions About Louisiana Bridges
How many bridges are in Louisiana?
Louisiana has 13K bridges in the FHWA National Bridge Inventory as of the 2025 federal release. 3.9K (31%) are classified as structurally deficient. The average bridge age is 44 years and the average BridgeWatch Condition Score is 53/100.
What does "structurally deficient" mean for Louisiana bridges?
A bridge is classified as structurally deficient when at least one of its three primary load-carrying components — deck, superstructure, or substructure — receives an NBI condition rating of 4 or lower on the 0-9 federal scale. This is a condition-based classification used by the Federal Highway Administration to determine eligibility for federal bridge replacement and rehabilitation funds. It does not mean a bridge is unsafe to cross at posted weight limits; it means the rating threshold for funding eligibility has been met.
Who inspects Louisiana's bridges?
Bridge inspections in Louisiana are conducted by the state department of transportation under the National Bridge Inspection Standards (NBIS). Federal regulation requires that every public-road bridge longer than 20 feet be inspected at least every 24 months by a certified team leader. Results are submitted to FHWA and aggregated into the National Bridge Inventory, the source for every number on this page.
How is the Louisiana Condition Score calculated?
The BridgeWatch Condition Score is a 0-100 composite that weights deck condition (33%), superstructure condition (33%), and substructure condition (34%), with an age penalty applied for bridges older than 50 years. The 0-9 NBI ratings are mapped to 0-100, summed, and rounded. Letter grades A through F are then assigned based on the composite score. See the methodology page for the full formula.
How often is Louisiana bridge data updated?
FHWA publishes a complete National Bridge Inventory annually, typically in the spring covering the prior calendar year of inspections. BridgeWatch refreshes Louisiana's page within a few days of each release. The current data reflects the 2025 NBI release, refreshed April 2026.