In the morning of August 11, 2015 an Arizona prison bus carrying 50 prison work crew inmates crashed into a semi-truck that had rolled over on Interstate 8, between Gila Bend and Casa Grande.
An inmate and an Arizona Department of Corrections employee were critically injured, other inmates received hospital treatment.
Inmates helped to direct traffic around the wreckage. The semi had jackknifed, blocking westbound lanes of I-8.
In jackknife crashes, if a vehicle towing a trailer skids, the trailer can push from behind until it spins around and faces backwards. The loss of control can be caused by equipment failure or improper braking.
Source: Arizona Republic, “Prison bus crashes on I-8,” Tom Tingle, August 12, 2015.