A 45-year-old Lecompton man was injured Friday morning when his motorcycle struck a road sign in northwestern Douglas County.

Lt. Kari Wempe, a sheriff’s department spokeswoman, said the man’s 1984 Harley Davidson ran off the pavement of County Road 1023 at 10:42 a.m. and then struck the sign.

He was flown by helicopter ambulance to the University of Kansas Hospital in Kansas City, Kan.

Wempe said the injured man was in critical condition when flown from the scene. She declined to name him because his family had not been notified.

The man, who was not wearing a helmet, was driving south on the road with a rider on another motorcycle who notified authorities, Wempe said. Officers are investigating alcohol as a possible contributing factor to the accident, she said.