A 20-year-old motorcyclist died in a single-vehicle collision in Hawaii Kai Tuesday night.

Honolulu police said the motorcyclist was traveling eastbound on Kalanianaole Highway when, for unknown reasons, he lost control and was thrown onto a sidewalk shortly before 8 p.m.

He was pronounced dead at the scene.

Police said he was wearing a helmet at the time of the crash.

Speed was a factor, police said. It’s unknown whether alcohol or drugs were factors.

Police closed the highway from Keahole Street to Lunalilo Home Road for several hours as they responded and investigated.

This was the 20th traffic-related fatality on Oahu this year compared with 18 at the same time last year.