Highway Accident Report

Adopted: June 13, 1974
AUTOMOBILE CRASH OFF THE
SILLIMAN EVANS BRIDGE, I-24/65,
NASHVILLE, TENNESSEE
July 27, 1973

NTSB Number: HAR-74/02
NTIS Number: PB-234406/AS


SYNOPSIS

Shortly before 5:45 a.m., on July 27, 1973 in a light ground fog or haze, a car crashed through the barrier system on the edge of the Silliman Evans Bridge, I-24/65, in Nashville, Tenn. There were nine persons in the automobile; seven passengers and the driver died. None of the occupants were ejected.

The automobile was traveling on the off-ramp from eastbound I-40 onto northbound I-24/65. When it reached the vicinity of the juncture of the two roadways, the car deviated from the pathway provided and struck the curb face of a raised concrete island. Impact with the island caused the driver to lose control of the automobile, which then traveled northeast across the two lanes of I-24/65 and struck and displaced a boxbeam guardrail located on a concrete curb in front of the bridge rail. As the right front wheel of the car struck and mounted the curb, the automobile moved forward with dynamic uplift, overrode the box-beam, plunged through the bridge rail, and fell 65 feet to the ground.

The pavement on the bridge was dry. There was no evidence of excessive speed, and no other traffic was present at the time of the crash. Alcohol was not involved.

The National Transportation Safety Board determines that the probable cause of this accident was the failure of the driver to maintain her vehicle in the pathway provided.

The following are contributing factors which may have confused the driver: (a) increasing curvature of the ramp; (b) narrowing of the ramp from two lanes to one; (c) a misleading traffic-control sign; (d) misleading pavement markings; and (e) an inadequately delineated and unnecessary section of a concrete island which narrowed the pathway to less than the width of a normal traffic lane--all in the last 600 feet of the ramp.

This confusion probably contributed to the striking of the concrete island, which caused loss of control of the automobile and its subsequent impact with the bridge rail barrier system.

The fall of the automobile to the ground and the resultant fatalities were caused by the failure of the barrier systems to retain or redirect the errant vehicle. Contributing to this failure were: (a) an unnecessary 9-inch-high curb, which provided the impacting vehicle with dynamic uplift; (b) improper installation of a box-beam median-type barrier system rather than a more rigid system; (c) redesign of the boxbeam mounting method, which did not secure the beam to its base; (d) inadequate maintenance of the box-beam; and (e) an outside bridge rail not adequate to withstand the vehicle impact.

The probable cause of the failure to detect and correct these hazards was the absence of a systematic program for the identification, surveillance, and correction of potential, or existing, hazardous conditions on the highway.

RECOMMENDATIONS

As a result of the investigation of this accidents the Safety Board on August 30, 1973, submitted three recommendations to the Governor of the State of Tennessee. (See Appendix C for a copy of the recommendation letter and the response of the State of Tennessee.) The Safety Board further recommends that:

1. The Federal Highway Administration:

(a) Establish national performance standards, including dynamic testing procedures, for bridge rail systems. Such standards should extend performance criteria to include impact by heavy vehicles and should improve performance characteristics for impacts by all classes of vehicles. The establishment of these standards should be of high priority and compliance should be mandatory for all new bridge rail systems used on public roadways. (Recommendation No. H-74-18).

(b) Assure that the State of Tennessee is maintaining Federal-aid highway projects in accordance with Federal law (U.S.C. Title 23, Section 116). (Recommendation No. H-74-19)

2. The State of Tennessee:

(a) Implement all the provisions of Federal Highway Safety Program Standard No. 9, "Identification and Surveillance of Accident Locations." and No. 12, "Highway Design, Construction and Maintenance." with special emphasis on the provisions relating to each State's having a systematically organized program to identify and correct potential or existing hazardous conditions within the highway right-of-way. (Recommendation No. H-74-20).

(b) Implement all the provisions of Federal Highway Safety Program Standard No. 18, "Accident Investigation and Reporting," with special emphasis on the provisions which require in-depth accident investigations by teams of two or more persons who represent a range of technical disciplines. (Recommendation No. H-74-21).