Structure 27 0072 · Marin County, CA

Tamalpais Drive over US Highway 101

Carries Tamalpais Drive over US Highway 101, 04-mrn-101-7.37-cmad.

Overall conditionFair

Set by its lowest-rated component: Deck at 5 of 9.

How ratings work
Decksets the rating5/9 · Fair
Superstructure7/9 · Good
Substructure7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT802 FT OVERALL100 FT0ELEVATION · LENGTHS TO SCALE
Deck 5/9 · sets the ratingSuperstructure 7/9Substructure 7/9

802 ft end to end, longest span 83 ft: about 2.2 football fields. 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.

Built1957rebuilt 1985
Length801.8 ft244.4 m
Daily traffic40,000counted 2003
Last inspectedMay 2024every 24 months

Location

StateCalifornia
CountyMarin
Location04-mrn-101-7.37-cmad
CarriesTamalpais Drive
CrossesUS Highway 101
Coordinates37.92537, -122.51592

Physical Characteristics

MaterialSteel
DesignStringer/Multi-beam
Total Length801.8 ft (244.4 m)
Max Span83.0 ft (25.3 m)
Deck Width63.6 ft (19.4 m)
Deck Area4741.4 sq m
Main Spans4
Year Built1957 (reconstructed 1985)

Traffic

Avg Daily Traffic40,000 (2003)
Truck Traffic1%
Lanes On Bridge4
Lanes Under Bridge10

Inspection & Ownership

Last InspectionMay 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure Number27 0072

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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