A 28-year-old Kailua-Kona woman was critically injured when the moped she was riding was run over Tuesday by a trailer in Kailua-Kona.

Hawaii County police said the woman was a passenger on a moped when the operator, a 21-year-old Kailua-Kona man, attempted to merge onto the southbound lane of Queen Kaahumanu Highway from Hualalai Road.

Police said the moped got between a dump truck and the trailer.

The trailer ran over the moped at about 10 a.m. Tuesday, police said.

Neither rider was wearing a helmet, police said.

Police said she suffered critical head injuries and was taken to the Kona Community Hospital. The moped driver received minor injuries, police said.

The truck driver was not injured.

Police have opened a negligent injury investigation into the crash.