US Bridges

Tamalpais Drive over US Highway 101

Fair

Marin County, California · 04-MRN-101-7.37-CMAD · Structure no. 27 0072

Built
1957
68 years old, rebuilt 1985
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
802 ft
4 main spans
Daily traffic
40,000
2003 count
Owner
State
State Highway Agency

About this bridge

Tamalpais Drive over US Highway 101 is a steel stringer/multi-beam or girder carrying Tamalpais Drive over US Highway 101 in Marin County, California. It was built in 1957 and reconstructed in 1985, so it is 68 years old, older than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 40,000 vehicles a day, roughly 1% of them trucks, projected to reach 88,106 by 2042. The structure is 802 ft (244.4 m) long and 64 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

Open in Google Maps
CarriesTamalpais Drive
CrossesUS Highway 101
Location04-MRN-101-7.37-CMAD
RouteCity Street 0
CountyMarin County
StateCalifornia
Coordinates37.92537, -122.51592
Functional classUrban Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment7: Better than present minimum criteria
Operating rating42.5 US tons
Inventory rating25.7 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans4 (+15 approach)
Design loadHS 20
Structure length802 ft (244.4 m)
Longest span83 ft (25.3 m)
Deck width64 ft (19.4 m)
Roadway width56 ft (17.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic40,000 (2003)
Projected traffic88,106 by 2042
Trucks1%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Tamalpais Drive over US Highway 101 built?

It was built in 1957, making it 68 years old in 2025. It was reconstructed in 1985.

What condition is Tamalpais Drive over US Highway 101 in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in May 2024.

How much traffic does Tamalpais Drive over US Highway 101 carry?

About 40,000 vehicles per day (2003 count), of which roughly 1% are trucks.

How long is Tamalpais Drive over US Highway 101?

The structure is 802 ft (244.4 m) long with a longest span of 83 ft (25.3 m) and a deck 64 ft wide.

Who owns Tamalpais Drive over US Highway 101?

It is owned by the State Highway Agency.