A Utah resident died in a collision on Interstate 80 near Rock Springs early Saturday, according to a news release from the Wyoming Highway Patrol on Monday.

Douglas Hazelton, 57, of Ogden, Utah, died at the scene, according to the news release.

Wyoming Highway Patrol troopers were dispatched to milepost 139 on I-80 for a two-vehicle collision at 1:16 a.m. Saturday.

Troopers determined a sedan driven by Hazelton was traveling westbound on Interstate 80 at a reduced rate of speed. The speeds were reported to be between 35 mph and 55 mph, and the sedan was weaving between both lanes of travel.

A semi-tractor also was westbound on the highway, came upon the sedan and was unable to avoid striking it from the rear.

Troopers are investigating driver impairment as a result of medication as a contributing factor to explain why the sedan was driven so erratically.

This marked the 66th fatality on Wyoming’s highways compared to 45 in 2016, and 66 in 2015.