U.S. HIGHWAY 101
U.S. HIGHWAY 101 in 04-Mrn-101-11.20-Srf, Marin County, California received a condition grade of F (0/100). Built in 1895, the bridge carries 129K vehicles daily on U.S. HIGHWAY 101 over Irwin Creek. It is classified as structurally deficient.
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 131-year-old bridge located 04-Mrn-101-11.20-Srf in Marin County, California. The bridge carries U.S. HIGHWAY 101 over Irwin Creek with 9 traffic lanes, handling approximately 129K vehicles per day. Built in 1895 and reconstructed in 1987, the structure spans 63 meters.
The bridge received a Condition Grade of F (0/100) based on Federal Highway Administration inspection data. Its deck is rated 0/9 (serious), superstructure 0/9 (serious), and substructure 0/9 (serious). The bridge is classified as structurally deficient, meaning at least one major component is rated 4 or below — this signals a need for repair or replacement but does not necessarily indicate an immediate safety hazard.
This bridge is owned and maintained by State Highway Agency.
Location Map
Frequently Asked Questions
U.S. HIGHWAY 101 has a Condition Score of 0/100 (Grade F). Its deck is rated 0/9, superstructure 0/9, and substructure 0/9 on the NBI scale. The bridge is classified as structurally deficient.
U.S. HIGHWAY 101 was built in 1895 and reconstructed in 1987, making it 131 years old. The average bridge age in the United States is 48 years.
U.S. HIGHWAY 101 carries approximately 129K vehicles per day (average daily traffic). The bridge has 9 traffic lanes. It is 63 meters long and located on U.S. HIGHWAY 101 in 04-Mrn-101-11.20-Srf, Marin County, California.
Yes, U.S. HIGHWAY 101 is classified as structurally deficient because at least one of its primary components (deck, superstructure, or substructure) is rated 4 or below on the 0-9 NBI scale. This does not necessarily mean it is unsafe, but it requires significant repair or replacement.
U.S. HIGHWAY 101 is located 04-Mrn-101-11.20-Srf in Marin County, California. The bridge carries U.S. HIGHWAY 101 over Irwin Creek. Its coordinates are 37.976886, -122.520264. It is maintained by State Highway Agency.
U.S. HIGHWAY 101 carries U.S. HIGHWAY 101 over Irwin Creek. The bridge is 63 meters long and was built in 1895, with reconstruction in 1987.
Condition Score is calculated from deck (33%), superstructure (33%), and substructure (34%) NBI ratings with an age penalty for bridges over 50 years.