The National Transportation Safety Board has found that a fatal highway crash in a work zone in Tennessee was caused by the truck driver's health problems and a flawed medical certification process.

The board also said that poor coordination and planning for the work zone project by the Tennessee Department of Transportation, the Tennessee Highway Patrol and the construction contractor contributed to the crash.
On July 26, 2000, an eastbound tractor-trailer traveling at a driver-estimated speed of 65 mph entered a 55-mph work zone and collided with a Tennessee Highway Patrol vehicle protecting the work zone. The patrol car exploded and caught fire as it was pushed nearly 200 feet before coming to rest on the median. The truck continued through the median and into the westbound lanes, where it collided with another vehicle. The trooper in the patrol car was killed in the crash. Witnesses saw the truck drifting out of its lane before the accident.
The truck driver had previously been diagnosed with sleep apnea and hypothyroidism, and had a similar crash in 1997, when he struck the rear of a patrol car in Utah.
Although neither condition is an automatic disqualification for getting a commercial driver's license, the NTSB believes that had a comprehensive medical oversight program been in place at the time of the accident, this driver would have been less likely to have been operating a commercial vehicle. This accident, the Board said, "demonstrates how easily unfit drivers are able to take advantage of the inadequacies of the current medical system, resulting in potentially fatal consequences."
The board urged the Federal Motor Carrier Safety Administration and the American Association of Motor Vehicle Administrators to act quickly to develop a comprehensive medical oversight plan for commercial drivers.
In addition, motorists had complained about the design of the work zone before the accident. The signage was poor and drivers were unsure which lane was closed. In fact, the board noted, the traffic control configuration for this work zone did not meet federal guidelines for a lane closure on a divided highway. The board also said that if the Tennessee Highway Patrol officers received work zone traffic control training, they may have asked for clarification on the traffic control strategy to be used that day, and would have realized the hazards of positioning their vehicles in the lane behind the highway construction vehicles.