A milk truck-tanker that triggered a crash on a Phoenix freeway in 2021 that killed four people and injured several others was caused by driver fatigue, U.S. transportation investigators said Tuesday.
In a virtual meeting to announce its probable cause report, the National Transportation Safety Board criticized Arizona Milk Transport for not ensuring drivers get adequate rest.
"Having a strong safety culture is more than just putting policies on paper, companies must live those policies from leadership to rank-and-file," NTSB Chair Jennifer Homendy said during the meeting. "I certainly hope this investigation served as a wake-up call for AMT (Arizona Milk Transport) and for the entire industry."
On the night of June 9, 2021, a combination truck and tanker carrying milk was on State Route 202 in Phoenix when it crashed into cars stopped for a road closure, hitting the last car in line. The tanker separated from the truck. The truck hit a concrete median, and it and another car caught fire.
Six cars in addition to the truck-tanker were involved in the crash.
Four people, ranging in age from 20-35, died. Eleven others were hurt. The driver was not injured.
Authorities ruled out alcohol, illegal substances or distractedness as factors.
The agency's investigation found video, records and other evidence that the truck driver had gotten little sleep the day of the crash. Video from a camera facing into the truck showed the driver looking forward for almost 10 seconds before the collision. However, there is no sign that he was aware of the "conspicuous" line of traffic coming up.
The driver also had an opportunity to get five to six hours of sleep earlier in the day. Instead, he had worked substantially more than 12 hours.
Under federal law, drivers transporting perishables like milk that are within 150 miles of their destination qualify for an agricultural exemption from limits on driving hours. Arizona Milk Transport had its own policy about maximum daily road hours, but it failed to enforce it, the NTSB said in a preliminary report. The NTSB found that the driver in the crash and others, in fact, regularly violated these policies and worked 70-80 hours a week.
"Just because something is legal doesn't mean it's safe," Homendy said. "Driving fatigue is deadly. Period."
The NTSB suggested Arizona Milk Transport create a program to make sure drivers follow policies and not become fatigued.
Their findings have prompted the NTSB to recommend the U.S. Department of Transportation examine the safety records of other carriers that take advantage of this exemption. Any findings could help shape proposals to Congress on how to improve driver safety.
There are also currently no federal requirements that semis have a standard of collision avoidance technology. If the truck or one of the other cars had sensors, cameras or wireless connectivity, investigators said it's likely the truck driver would have been alerted in time to prevent a crash or mitigate its impact.