Total bridges
360
Public highway bridges in St. Tammany County
County profile · official public datasets
St. Tammany County, LA
360 public highway bridges tracked in the FHWA National Bridge Inventory: 33.3% rated Good, 60.6% Fair, 6.1% Poor.
- 360
- Public bridges
- 33.3%
- Good condition
- 6.1%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
St. Tammany County pairs a top-quartile lowest Poor-condition share among rated counties in the state with an older average build year than the state inventory.
- Top 14%
- lowest Poor share in state
- 6.1%
- Poor-condition share
- 360
- public highway bridges
- 1976
- avg year built
Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.
St. Tammany County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, St. Tammany County ranks #9 of 64 Louisiana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.1%). St. Tammany County, Louisiana contains 360 public highway bridges. Roughly 33.3% are rated “Good,” 60.6% “Fair,” and 6.1% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.
Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.
Source: FHWA National Bridge Inventory. See methodology for full definitions.
Good condition
33.3%
120 of 360 rated 7-9
Fair condition
60.6%
218 of 360 rated 5-6
Poor condition
6.1%
22 of 360 rated 4 or below
In-state Poor-share rank
#9 of 64
Among Louisiana counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 360 NBI-tracked bridges by lowest applicable component rating.
Good 33.3% (120)
Fair 60.6% (218)
Poor 6.1% (22)
St. Tammany County's Poor-condition bridges carry 73,574 vehicle crossings a day
That is 1.6% of the county's reported daily bridge traffic on 6.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 3,504 crossings a day against 12,276 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.
Computed over the 342 of 360 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
50% of St. Tammany County's bridges have passed the 50-year mark
180 of the 360 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 33.3% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.
Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.
One structure carries 39.3% of the county's Poor-condition bridge traffic
US0190 over US190B/LA21/Bouge Falaya, built 1958, carries 28,900 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 22-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 73,574 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When St. Tammany County's bridges were built
360 bridges with a recorded construction year, grouped by decade
- 1930s 32
1930–1939
32 bridges
- 1940s 1
1940–1949
1 bridges
- 1950s 31
1950–1959
31 bridges
- 1960s
1960–1969
59 bridges
- 1970s
1970–1979
103 bridges
- 1980s 41
1980–1989
41 bridges
- 1990s
1990–1999
42 bridges
- 2000s 10
2000–2009
10 bridges
- 2010s 33
2010–2019
33 bridges
- 2020s 8
2020–2029
8 bridges
What this shows Construction peaked in the 1970s, when 103 of the county's bridges still in the inventory were built, which is 28.6% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1976, 6 years older than the Louisiana average of 1982.
How St. Tammany County compares with Louisiana's closest counties by inventory size
The 5 Louisiana counties nearest St. Tammany County in number of bridges, with their condition splits. Its 6.1% Poor share is the 2nd-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1983 is 7 years older.
Showing the 5 closest of 63 Louisiana counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Orleans County | 382 | 43.7% | 46.3% | 9.9% | 1976 |
| Jefferson County | 379 | 58.6% | 36.9% | 4.5% | 1984 |
| St. Tammany County (this page) | 360 | 33.3% | 60.6% | 6.1% | 1976 |
| Vernon County | 341 | 57.8% | 34.6% | 7.6% | 1989 |
| Ouachita County | 337 | 27.9% | 59.3% | 12.8% | 1981 |
| Lafayette County | 322 | 44.7% | 47.5% | 7.8% | 1986 |
Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to St. Tammany County's. Source: FHWA National Bridge Inventory, 2024 release.
Nationwide counties with similar inventory size or average build year
Two NBI-derived peer sets for St. Tammany County, both outside Louisiana so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside LA (360 bridges here).
- Polk County, FL · 360 bridges
- San Mateo County, CA · 361 bridges
- Washita County, OK · 361 bridges
- Richland County, SC · 361 bridges
Similar average build year
Nearest mean year-built outside LA (1976 here).
- Marion County, IN · avg 1976 · 958 bridges
- Mohave County, AZ · avg 1976 · 641 bridges
- Comanche County, OK · avg 1976 · 593 bridges
- Prince George's County, MD · avg 1976 · 576 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Poor-condition bridges (22)
LA0016
PoorOver: DRAIN
2.5 M W OF LA 21, St. Tammany, LA
Built 1968 Load: 0.0 t ADT: 1,388
DIXIE RANCH RD.
PoorOver: I-12
4.2 M E OF LA 434, St. Tammany, LA
Built 1972 Load: 0.0 t ADT: 4,450
Hosmer Mill Rd
PoorOver: BR. OV BOGUE FALAYA RIVE
2 MI NE OF LA 437, St. Tammany, LA
Built 1980 Load: 0.0 t ADT: 839
Million Dollar Rd
PoorOver: BOGUE FALAYA RIVER
0.10 MI EAST OF LA 25, St. Tammany, LA
Built 1960 Load: 0.0 t ADT: 1,768
LA1077
PoorOver: BLACK BAYOU
1.1 M S OF LA 22, St. Tammany, LA
Built 1965 Load: 0.9 t ADT: 1,019
US0090
PoorOver: EAST PEARL RIVER
US0090, St. Tammany, LA
Built 1934 Load: 9.1 t ADT: 1,215
LA1129
PoorOver: SIMALUSA CREEK
2.3 M N OF LA 40, St. Tammany, LA
Built 1956 Load: 10.0 t ADT: 2,611
Lock # 3 Rd
PoorOver: CREEK
RT 778 1.55 MI E OF, St. Tammany, LA
Built 1960 Load: 11.0 t ADT: 100
US0090
PoorOver: WEST MIDDLE RIVER
1.9 mi NE of US 190, St. Tammany, LA
Built 1933 Load: 11.7 t ADT: 1,215
US0090
PoorOver: MIDDLE MIDDLE PEARL RIVE
2.4 miles east of US 190, St. Tammany, LA
Built 1933 Load: 13.0 t ADT: 1,215
US0090
PoorOver: E MIDDLE PEARL RIVER
3 miles east of US 190, St. Tammany, LA
Built 1933 Load: 13.0 t ADT: 1,215
LA0059
PoorOver: LONG BRANCH BAYOU
0.5 M N OF LA 36, St. Tammany, LA
Built 1954 Load: 15.9 t ADT: 4,612
Keller Rd
PoorOver: CREEK
0.3MI.N.OF 9TH STREE, St. Tammany, LA
Built 1970 Load: 15.9 t
US0011
PoorOver: NO&NE RAILROAD
1.05 MI S OF I-12 EB, St. Tammany, LA
Built 1937 Load: 16.5 t ADT: 15,607
Tiger branch
PoorOver: BR. OVER TIGER BRANCH
1.40 EAST OF LA 25, St. Tammany, LA
Built 1987 Load: 16.5 t ADT: 300
CHRIS KENNEDY RD
PoorOver: GUM CREEK
1.32 MI. SOUTH OF LA 41, St. Tammany, LA
Built 1984 Load: 17.5 t ADT: 848
LA0036
PoorOver: ABITA RIVER
0.1 M E OF LA 59, St. Tammany, LA
Built 1957 Load: 18.5 t ADT: 1,844
Rousseau Rd
PoorOver: TCHEFUNETE RIVER
0.45 MILES NORTH OF LA.10, St. Tammany, LA
Built 1973 Load: 19.8 t ADT: 458
N. Blvd.
PoorOver: CANAL
1.0 MILE SOUTH OF I 12 OF, St. Tammany, LA
Built 1974 Load: 20.1 t ADT: 500
US0090
PoorOver: WEST PEARL RIVER
US0090, St. Tammany, LA
Built 1933 Load: 21.1 t ADT: 1,215
US0190
PoorOver: US190B/LA21/Bouge Falaya
US0190, St. Tammany, LA
Built 1958 Load: 49.9 t ADT: 28,900
N. Wllie Rd
PoorOver: DRAINAGE DITCH
2.2 M NORTH OF LA 1077, St. Tammany, LA
Built 1990 Load: 74.5 t ADT: 2,255
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.