U.S. HIGHWAY 101
U.S. HIGHWAY 101 in 04-Mrn-101-8.02-Cmad, Marin County, California received a condition grade of C (58/100). Built in 1929, the bridge carries 172K vehicles daily on U.S. HIGHWAY 101 over Wornum Drive.
U.S. HIGHWAY 101 carries a C on the BridgeSafety Condition Score with 58/100. Component ratings sit in the middle of the FHWA NBI distribution; rehabilitation programming is likely on the owning agency’s medium-term horizon.
The bridge was built in 1929, making it 97 years old — well beyond the typical 50-year design life of bridges constructed in that era. Bridges of this vintage usually need substantial rehabilitation or replacement once their original components have aged out, regardless of current condition ratings. U.S. HIGHWAY 101 carries an average daily traffic count of 172,000 vehicles, with 8 lane(s) crossing Wornum Drive. The owning agency is State Highway Agency; bridge inspection records flow into the federal NBI database annually.
Component Ratings
The riding surface, evaluated for cracking, spalling, and wear
Beams, girders, and trusses that support the deck
Piers, abutments, and foundations below the deck
Bridge Details
About This Bridge
U.S. HIGHWAY 101 is a 97-year-old bridge located 04-Mrn-101-8.02-Cmad in Marin County, California. The bridge carries U.S. HIGHWAY 101 over Wornum Drive with 8 traffic lanes, handling approximately 172K vehicles per day. Built in 1929 and reconstructed in 1975, the structure spans 43 meters.
The bridge received a Condition Grade of C (58/100) based on Federal Highway Administration inspection data. Its deck is rated 7/9 (good), superstructure 7/9 (good), and substructure 7/9 (good).
This bridge is owned and maintained by State Highway Agency.
Location Map
Frequently Asked Questions
U.S. HIGHWAY 101 has a Condition Score of 58/100 (Grade C). Its deck is rated 7/9, superstructure 7/9, and substructure 7/9 on the NBI scale. The bridge is not classified as structurally deficient.
U.S. HIGHWAY 101 was built in 1929 and reconstructed in 1975, making it 97 years old. The average bridge age in the United States is 48 years.
U.S. HIGHWAY 101 carries approximately 172K vehicles per day (average daily traffic). The bridge has 8 traffic lanes. It is 43 meters long and located on U.S. HIGHWAY 101 in 04-Mrn-101-8.02-Cmad, Marin County, California.
No, U.S. HIGHWAY 101 is not classified as structurally deficient. All three primary components (deck, superstructure, and substructure) are rated above 4 on the 0-9 NBI scale.
U.S. HIGHWAY 101 is located 04-Mrn-101-8.02-Cmad in Marin County, California. The bridge carries U.S. HIGHWAY 101 over Wornum Drive. Its coordinates are 37.935322, -122.516483. It is maintained by State Highway Agency.
U.S. HIGHWAY 101 carries U.S. HIGHWAY 101 over Wornum Drive. The bridge is 43 meters long and was built in 1929, with reconstruction in 1975.
Condition Score is calculated from deck (33%), superstructure (33%), and substructure (34%) NBI ratings with an age penalty for bridges over 50 years.
Source: FHWA National Bridge Inventory, 2026.