Structure 180430054903227 · Collin County, TX

SH 121 SB over Dart

Carries SH 121 SB over Dart, 1 Mi N Of Melissa.

Overall conditionFair

Set by its lowest-rated component: Deck at 6 of 9.

How ratings work
Decksets the rating6/9 · Satisfactory
Superstructure7/9 · Good
Substructure7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT307 FT OVERALL50 FT0ELEVATION · LENGTHS TO SCALE
Deck 6/9 · sets the ratingSuperstructure 7/9Substructure 7/9

307 ft end to end: about 4 semi-trucks nose to tail. Lengths and the semi-truck on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a multi-beam bridge.

Built20188 years old
Length307.1 ft93.6 m
Daily traffic16,527counted 2011
Last inspectedMay 2023every 24 months

Location

StateTexas
CountyCollin
Location1 Mi N Of Melissa
CarriesSH 121 SB
CrossesDart
Coordinates33.27488, -96.57615

Physical Characteristics

MaterialPrestressed Concrete
DesignStringer/Multi-beam
Total Length307.1 ft (93.6 m)
Max Span127.0 ft (38.7 m)
Deck Width40.0 ft (12.2 m)
Deck Area1141.9 sq m
Main Spans1
Year Built2018

Traffic

Avg Daily Traffic16,527 (2011)
Truck Traffic13%
Lanes On Bridge2

Inspection & Ownership

Last InspectionMay 2023
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure Number180430054903227

How Bridge Ratings Work

Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."

0Failed
1Imminent failure
2Critical
3Serious
4Poor
5Fair
6Satisfactory
7Good
8Very good
9Excellent
Good · lowest component 7–9
Fair · lowest component 5–6
Poor · lowest component 0–4

A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.

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