Witnesses told police a motorcyclist was speeding and weaving in and out of traffic on Fort Weaver Road before a fatal crash at about 5:30 a.m. Thursday.

The motorcyclist, a 27-year-old Ewa Beach man, died at the crash scene near the recently closed Hawaii Medical Center-West. The Army said the man, whose name was withheld pending notification of next of kin, was a soldier stationed at Schofield Barracks.

The crash closed the northbound lanes of Fort Weaver Road, the main artery from Ewa Beach. Police reopened the road at 8:05 a.m.

The 2009 Yamaha motorcycle appeared to have sideswiped a 2001 Nissan sedan near the Farrington Highway junction, causing the motorcyclist to lose control, said Lt. Robert Towne of the police traffic investigations division.

The motorcyclist was thrown from the vehicle and slid about 30 feet into a guardrail, severing his arm, Towne said.

The motorcycle also hit the guardrail, traveled another 100 feet and came to rest near the Farrington Highway overpass, he said.

The victim was wearing a helmet, Towne said.

The fatality was the first traffic death of 2012 on Oahu, compared with three at this time last year.