A moped rider was declared dead Sunday after he crossed the centerline of Kalanianaole Highway near Makapuu Lighthouse and collided head-on with a motorcycle, police said.

The motorcyclist, a member of the military, 31, was taken to the Queen’s Medical Center in critical condition. His passenger, a 40-year-old female tourist, was taken to Queen’s in serious condition.

She was the only one wearing a helmet, said police.

The crash happened as the rented moped was traveling downhill toward Hawaii Kai where the roadway curves to the right, police said. The motorcycle, a 2011 Harley-Davidson, was coming from the other direction.

Police said the moped rider, a 36-year-old tourist, might have been speeding.

It was not immediately known if alcohol was a factor.

The crash occurred at 11:55 a.m. about a quarter-mile south of the Ka Iwi Trail, also known as the Makapuu Lighthouse Trail.

Police closed the road between Kealahou Street and the Makapuu Lighthouse to investigate. The road reopened shortly before 4 p.m.

This was the 31st traffic fatality on Oahu’s roadways so far this year, compared to 24 for the same period last year.