US Bridges

Md 478 over Br of Potomac River

Fair

Frederick County, Maryland · 0.23 Mile East of Md 180 · Structure no. 100000100088010

Built
1926
99 years old
Condition
Fair
inspected June 2024
Type
Tee Beam
Concrete
Length
26 ft
1 main span
Daily traffic
2,471
2009 count
Owner
State
State Highway Agency

About this bridge

Md 478 over Br of Potomac River is a concrete tee beam carrying Md 478 over Br of Potomac River in Frederick County, Maryland. It was built in 1926, so it is 99 years old, older than the Maryland average of 52.6 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 2,471 vehicles a day, roughly 8% of them trucks, projected to reach 3,506 by 2026. The structure is 26 ft (7.9 m) long and 26 ft wide. If it were closed, the detour would be 8.1 mi (13 km).

Location

Open in Google Maps
CarriesMd 478
CrossesBr of Potomac River
Location0.23 Mile East of Md 180
RouteState Highway 478
CountyFrederick County
StateMaryland
Coordinates39.32508, -77.66235
Functional classUrban Minor Arterial

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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating48.5 US tons
Inventory rating29 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length26 ft (7.9 m)
Longest span24 ft (7.3 m)
Deck width26 ft (7.9 m)
Roadway width24 ft (7.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,471 (2009)
Projected traffic3,506 by 2026
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.1 mi (13 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedWidening of existing bridge without deck rehabilitation
Estimated improvement cost$44,000
NavigationNo navigation control on waterway

Frequently asked questions

When was Md 478 over Br of Potomac River built?

It was built in 1926, making it 99 years old in 2025.

What condition is Md 478 over Br of Potomac River 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 June 2024.

How much traffic does Md 478 over Br of Potomac River carry?

About 2,471 vehicles per day (2009 count), of which roughly 8% are trucks.

How long is Md 478 over Br of Potomac River?

The structure is 26 ft (7.9 m) long with a longest span of 24 ft (7.3 m) and a deck 26 ft wide.

Who owns Md 478 over Br of Potomac River?

It is owned by the State Highway Agency.