A serious ATV crash is under investigation in Fort Irwin. Haliburton Highlands OPP says a 64 year old Haliburton man was driving a 1996 Honda ATV on Harburn Road near Dunn Road around 7pm Saturday night when he collided with a tree. Police add he was not wearing a helmet and he sustained life threatening injuries.  He was transported by ambulance to Haliburton hospital and then relocated to a Toronto area hospital by air ambulance. His name has not been released.