​​On June 25, 2015, about 7:10 p.m., a 2007 Peterbilt truck-tractor in combination with a 2005 Great Dane semitrailer, operated by Cool Runnings Express, Inc., was traveling northbound in the center lane of Interstate 75, near Chattanooga, Tennessee, when the driver did not respond to the slow-moving traffic ahead and collided with the rear of a 2010 Toyota Prius. Traffic had slowed near milepost 11.7 because of road construction and a work zone lane closure at milepost 12. The truck-tractor continued forward and collided with seven additional vehicles, forcing them into subsequent collisions. Of the 18 vehicle occupants, six died and four were injured. A postcrash fire consumed one vehicle. The truck driver’s trip began earlier that day, about 5:16 a.m., in Haines City, Florida. His destination was the carrier terminal in London, Kentucky.

We determined that the probable cause of the Chattanooga, Tennessee, crash was the truck driver’s failure to respond to the slow-moving traffic within a work zone because of performancdecrements likely associated with his fatigue and methamphetamine use. Contributing to the crash was the failure of the pre-employment screening process to identify driver risk factors. Contributing to the severity of the crash was the truck-tractor’s high impact speed.

The investigation identified the following safety issues:

• Truck driver’s performance: The truck driver did not respond to the slowed traffic and the formation of the traffic queue. His lack of evasive steering maneuvers or emergency braking indicates a performance decrement, which was likely associated with fatigue and methamphetamine use.
• Limitations of current drug testing program: National Transportation Safety Board (NTSB) investigators reviewed the truck driver’s toxicology test results from a variety of sourcesincluding a urine test, a hair test, and a postcrash blood test. The test results indicated a pattern of drug use not identified by the US Department of Transportation drug testing program. This investigation reaffirmed the need to gather data on the prevalence of commercial motor vehicle (CMV) driver use of impairing substances and to consider alternative drug testing methods.
• Inadequacies of driver license records and background checks: The commonwealth of Kentucky is one of only two US jurisdictions that do not provide crash data in their 3-year driver license records. Consequently, Cool Runnings Express did not have crash data for the truck driver, limiting its ability to assess his safety performance and potential risk. The driver had had four crashes in the previous 3 years, two of which were CMV crashes.
• Truck overrepresentation in work zone crashes: Although trucks account for 11.4 percent of all fatal crashes, they are involved in 30.1 percent of fatal work zone crashes. Speeding, distraction, and impairment are key factors in these crashes. To improve work zone safety, local agencies can take more proactive actions with regard to procedures and training for law enforcement presence and control. At the national level, additional guidance can be developed for the use of supplemental traffic control strategies to mitigate work zone crashes involving trucks or heavy vehicles.

We made recommendations to the Federal Motor Carrier Safety Administration (FMCSA), the Kentucky Transportation Cabinet and the Idaho Transportation Department, and the Tennessee Department of Transportation and the Tennessee Highway Patrol. We also reiterated one recommendation to the Federal Highway Administration, and reiterates and reclassifies one recommendation to the FMCSA.