US Bridges

Main Gate Road over Smart Railroad

Fair

Marin County, California · 0.37 MI E HWY 101 · Structure no. 27C0164

Built
1930
95 years old, rebuilt 1995
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
141 ft
4 main spans
Daily traffic
5,000
2016 count
Owner
County
County Highway Agency

About this bridge

Main Gate Road over Smart Railroad is a steel continuous stringer/multi-beam or girder carrying Main Gate Road over Smart Railroad in Marin County, California. It was built in 1930 and reconstructed in 1995, so it is 95 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 6 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 5,000 vehicles a day, roughly 5% of them trucks, projected to reach 6,141 by 2042. The structure is 141 ft (43.1 m) long and 39 ft wide. If it were closed, the detour would be 0.6 mi (1 km).

Location

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CarriesMain Gate Road
CrossesSmart Railroad
Location0.37 MI E HWY 101
RouteCity Street 0
CountyMarin County
StateCalifornia
Coordinates38.05529, -122.52359
Functional classRural Minor Collector

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating28.2 US tons
Inventory rating17.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadUnknown
Structure length141 ft (43.1 m)
Longest span35 ft (10.7 m)
Deck width39 ft (11.9 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic5,000 (2016)
Projected traffic6,141 by 2042
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesRailroad
Detour if closed0.6 mi (1 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Main Gate Road over Smart Railroad built?

It was built in 1930, making it 95 years old in 2025. It was reconstructed in 1995.

What condition is Main Gate Road over Smart Railroad 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 September 2024.

How much traffic does Main Gate Road over Smart Railroad carry?

About 5,000 vehicles per day (2016 count), of which roughly 5% are trucks.

How long is Main Gate Road over Smart Railroad?

The structure is 141 ft (43.1 m) long with a longest span of 35 ft (10.7 m) and a deck 39 ft wide.

Who owns Main Gate Road over Smart Railroad?

It is owned by the County Highway Agency.