A tractor trailer jackknifed across four lanes of Interstate 40 early Tuesday morning.
The accident occurred around 12:50 a.m. at mile marker 211 on the east side of the downtown loop.
Officials said the driver may have suffered from a medical condition and veered left off the eastbound roadway, causing his truck to block all four lanes of westbound traffic.
The driver was taken to the hospital. His injuries are considered life-threatening.
The tractor trailer never hit another vehicle and never turned over.
Westbound lanes were closed until just after 3 a.m.