IS 55 S
IS 55 S in S 4 T 43 N R 6 E, St. Louis County, Missouri received a condition grade of F (0/100). Built in 1964, the bridge carries 158K vehicles daily on IS 55 S over Mattese CR. It is classified as structurally deficient.
IS 55 S carries an F on the BridgeSafety Condition Score with 0/100 — the bottom tier of the FHWA NBI distribution. Component ratings flag the structure for near-term rehabilitation or replacement; the bridge may remain open to traffic but is on the priority list for action.
The bridge was built in 1964 and is now 62 years old, at or past the typical 50-year design life for bridges of its vintage. Maintenance and inspection cycles are correspondingly more involved than for newer structures. IS 55 S carries an average daily traffic count of 157,561 vehicles, with 12 lane(s) crossing Mattese CR. 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
IS 55 S is a 62-year-old bridge located S 4 T 43 N R 6 E in St. Louis County, Missouri. The bridge carries IS 55 S over Mattese CR with 12 traffic lanes, handling approximately 158K vehicles per day. Built in 1964 and reconstructed in 1995, the structure spans 6.7 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
IS 55 S 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.
IS 55 S was built in 1964 and reconstructed in 1995, making it 62 years old. The average bridge age in the United States is 48 years.
IS 55 S carries approximately 158K vehicles per day (average daily traffic). The bridge has 12 traffic lanes. It is 6.7 meters long and located on IS 55 S in S 4 T 43 N R 6 E, St. Louis County, Missouri.
Yes, IS 55 S 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.
IS 55 S is located S 4 T 43 N R 6 E in St. Louis County, Missouri. The bridge carries IS 55 S over Mattese CR. Its coordinates are 38.492114, -90.350483. It is maintained by State Highway Agency.
IS 55 S carries IS 55 S over Mattese CR. The bridge is 6.7 meters long and was built in 1964, with reconstruction in 1995.
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.