Highway Accident Report

Adopted: April 22, 1976
FEBRUARY 23, 1975

NTSB Number: HAR-76/03
NTIS Number: PB-253359/AS


About 9:25 p.m. on February 23, 1975, an automobile struck a vital structural member of the Yadkin River Bridge near Siloam, North Carolina. The collision occurred in heavy fog. Following the impact, the bridge collapsed and both the automobile and the bridge fell into the river. Six more vehicles vaulted into the collapse zone within a 17-minute period. Four-persons were killed and 16 were injured.

The National Transportation Safety Board determines that the probable cause of the bridge collapse was the penetration of the timber railing by the vehicle and its subsequent impact with and crushing of a vital MP structural member of the bridge truss. The timber railing was not adequate to sustain impact at posted speeds.


As a result of its investigation of this accident, the National Transportation Safety Board submitted the following recommendations to the Secretary of Transportation:

"Develop and publish, as a part of the FHWA research program, guidelines for the structural retrofit of bridge railings on existing bridge structures to protect vital structural members from impact by vehicles.

"Include under the National Bridge Inspection Standards and under Highway Safety Program Standard No. 12, 'Highway Design, Construction and Maintenance,' a requirement that bridge inspection reports be analyzed and evaluated within a specified time period, and that any changes in load limits be posted promptly.

"Include under Highway Safety Program Standard 12, 'Highway Design, Construction and Maintenance,' a requirement that all bridges on public roadways be inspected for safety under the same criteria established for bridges on the Federal-aid system under the National Bridge Inspection Standard.

"Institute a program in cooperation with the States which provides for the investigation, by multidisciplinary accident investigation teams, of the following:

a. All bridge collapses on public roadways,

b. Accidents involving vehicles that have struck traffic barrier railings on bridges and damaged structural members vital to the bridge's stability.

The number of such investigations should be sufficient to identify how such characteristics affect the severity of accidents.

"In cooperation with the States, perform a sufficient quantity of skid tests on timber roadway surfaces to establish if such surfaces can normally meet the recommended skid number values contained under Highway Safety Program Standard 12, 'Highway Design, Construction and Maintenance.'"