US Bridges

Mo 21 S over Rt Bb

Good

Jefferson County, Missouri · S 33 T 41 N R 4 E · Structure no. 29643

Built
2003
22 years old
Condition
Good
inspected December 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete Continuous
Length
170 ft
3 main spans
Daily traffic
9,327
2024 count
Owner
State
State Highway Agency

About this bridge

Mo 21 S over Rt Bb is a prestressed concrete continuous stringer/multi-beam or girder carrying Mo 21 S over Rt Bb in Jefferson County, Missouri. It was built in 2003, so it is 22 years old, younger than the Missouri average of 45.1 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 9,327 vehicles a day, roughly 9% of them trucks, projected to reach 17,255 by 2044. The structure is 170 ft (51.8 m) long and 41 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

CarriesMo 21 S
CrossesRt Bb
LocationS 33 T 41 N R 4 E
RouteState Highway 21
Coordinates38.238, -90.5776
Functional classRural Principal Arterial - Other

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure8 Very GoodNo problems noted.
Last inspectionDecember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating90.3 US tons
Inventory rating53.6 US tons

Structure

MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 25 or greater
Structure length170 ft (51.8 m)
Longest span58 ft (17.7 m)
Deck width41 ft (12.4 m)
Roadway width38 ft (11.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic9,327 (2024)
Projected traffic17,255 by 2044
Trucks9%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

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 Mo 21 S over Rt Bb built?

It was built in 2003, making it 22 years old in 2025.

What condition is Mo 21 S over Rt Bb in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in December 2024.

How much traffic does Mo 21 S over Rt Bb carry?

About 9,327 vehicles per day (2024 count), of which roughly 9% are trucks.

How long is Mo 21 S over Rt Bb?

The structure is 170 ft (51.8 m) long with a longest span of 58 ft (17.7 m) and a deck 41 ft wide.

Who owns Mo 21 S over Rt Bb?

It is owned by the State Highway Agency.