PORTLAND — A motorcyclist is in critical condition following a crash on Johnson Road that snarled traffic near the Portland Jetport.

The man was riding a Harley Davidson inbound on Johnson Road at 1:20 p.m. when it appears a Toyota Avalon driven by William Lyons, 83, of South Portland, tried to make a U-turn in front of him, police said.

The motorcycle hit the front left of the car and the rider was thrown from the motorcycle. The rider was taken to Maine Medical Center with serious head injuries.

The inbound and outbound lanes of Johnson Road are separated there and cars leaving City Line Drive often turn right onto Johnson Road inbound then make a U-turn when the lanes are no long separated to head outbound toward South Portland or Scarborough.

Police are not releasing the name of the motorcycle rider until family members have been notified.

The scene of the crash remained blocked off two hours later as police reconstructed the crash.

The motorcyclist was not wearing a helmet, police said.