A Prosser man was found unconscious inside a pickup that rolled on Interstate 82 near Prosser about 2 p.m. Tuesday.
Silbestre Dimas, 52, the driver of a Ford F-150 pickup, was headed west, according to the Washington State Patrol.
He lost control of the pickup, and it rolled into the median and came to rest on its wheels in the eastbound lanes of the interstate, according to the state patrol.
The state patrol continues to investigate, but said that equipment failure likely caused the crash.
Dimas was taken to Kadlec Regional Medical Center in Richland.
One eastbound lane of the interstate was closed as police investigated Tuesday afternoon, but it was expected to reopen to traffic about 4 p.m.