A serious accident involving a motorcycle along the Palisades Parkway Friday left the driver in extremely critical condition.A passerby found the victim on the northbound side of the roadway in Pomona just before 6 a.m. and called police. Police say they believe the motorcyclist may not have been wearing a helmet. The driver suffered serious head and neck injuries. He was unconscious when the ambulance arrived and was taken to Westchester Medical Center.