A semi-trailer travelling the wrong way down Edmonton's Yellowhead Trail crashed and toppled off an overpass Monday, bursting into flames.

The semi's male driver was pronounced dead at the scene shortly after the fiery crash, said police.

Police said they began receiving reports at about 1 p.m. about the semi around Highway 44, about 30 kilometres west of city limits, causing other vehicles to veer off the road to avoid it, said acting Insp. Todd Laycock.

Then police got calls that the tractor-trailer was going eastbound in the westbound lanes of the busy Yellowhead Trail freeway.

Around 178th Street, the semi hit a guard rail, rolled off the overpass onto railway tracks below and burst into flames.

"I don't know if we can explain it yet. We're early on in the investigation," said Laycock.

Donna Giberson was driving home to her acreage west of Edmonton when the eastbound tractor-trailer sped toward her.

"I was concentrating on the guy in front of me because once he went towards the ditch I thought: 'If I'm gonna live, I gotta hit the ditch,'" she said.

Giberson avoided the semi, but was then rear-ended by the driver of the pickup who followed her into the ditch. She said the incident left her shaking for about half an hour.

Tow truck drivers said several drivers were either rear-ended or sideswiped as they tried to avoid the semi's path.