PHOENIX – Federal security officials said Thursday they will investigate a crash in which authorities said a speeding milk tanker collided with seven cars on a highway in Phoenix, killing four people and injuring at least nine.
The wreck occurred late Wednesday after the tanker “did not slow down due to traffic congestion,” the Arizona Department of Public Safety said in a statement.
The National Transportation Safety Board said it sent nine investigators to conduct a safety probe into the crash in partnership with Arizona’s public safety department.
Among the questions that NTSB investigators will investigate is whether the crash could have been prevented if the tanker had been equipped with electronic safety devices, spokesman Chris O̵
Six of the nine people injured in the crash were taken to hospitals in critical condition, the Phoenix Fire Department said in a statement. The four men and two women were aged 22 to 45 years. Information about the four killed was not immediately released.
After the initial collisions, the trailer separated from the tanker rig and went over the median wall of the highway and ended up on the side of the tracks in the opposite direction, the public safety department said.
Authorities ruled out the possibility that the truck was deteriorating, the department said. The truck was not identified.
At present, there are no federal requirements for semis to have collision warning ahead or automatic emergency braking, although the systems will become common on smaller passenger cars.
The systems use cameras and sometimes radar to see objects in front of a vehicle, and they either warn the driver or brake and even stop the vehicle if it is about to hit something.
O’Neil said investigators will determine if the tanker had any advanced safety equipment, and if so, how it worked in the crash. If it did not have the systems, they would determine if “collision technology would have mitigated the severity or completely prevented it,” he said.
The NTSB, he said, has investigated several crashes in which large trucks hit stopped or slowed traffic. As early as 2015, the NTSB recommended that manufacturers immediately include electronic security systems as standard equipment. At the time, the agency said the systems could prevent or mitigate more than 80% of rear-end collisions, causing about 1,700 deaths and half a million injuries annually.
Twenty automakers, representing 99% of new passenger car sales in the United States, signed a voluntary agreement with the government in 2016 to make the feature standard on all light vehicles by September 1, 2022, and many companies are moving toward that goal.
O’Neil said the team heading to the collision scene included members with experience in motor carriers, highway design, passenger protection, human performance, vehicle factors and technical collision reconstruction.
Investigators will also try to determine if the driver’s distraction played a role, he said.
“Our investigators will look at the people involved in the accident, the vehicles involved in the accident, and the environment in which the accident occurred,” O’Neil said.
Investigators generally remain on site for five to ten days, and they publish a preliminary report 30 to 90 days after the completion of their fieldwork. Surveys usually take 12 to 24 months to complete.