ACT Policing was called to the scene at 7.40am after the vehicle hit a tree.

Uriarra Road was closed between Uriarra Village and Denman Prospect for several hours, and re-opened about noon.

Superintendent Corey Heldon said the major crash unit was investigating the circumstances of the crash but there had been no adverse weather conditions at the time.

"ACT Ambulance Service attended and attempted to resuscitate. Unfortunately he died at the scene," she said.

The silver twin cab Holden Rodeo was travelling towards Canberra at the time of the crash. Police are notifying the next of kin.

Superintendent Heldon said police had spoken to some people but there were no known witnesses to the crash.

"If anyone did witness the collision, contact police or Crimestoppers."

They have also asked anyone who drove between Uriarra Crossing and Denman Prospect from 7.15am to 8am to contact Crimestoppers on 1800 333 000, or at the website and quote reference 6636573.

Superintendent Heldon reminded motorists to slow down and make a plan for their journeys ahead of the October school holiday period.

"It's our fifth fatal on the road in the ACT this year. Every fatal is one too many so we'd like to remind everyone to be as safe as possible on the road."

She said assistance would be provided to the first responders who attended the crash.