A 49-year-old man, who was not wearing a helmet while speeding on a motorcycle, died early Thursday morning after he collided with a vehicle on the westbound H-1 freeway in Pearl City, police said.

Honolulu police arrested the driver of the vehicle, a 22-year-old man from Ewa Beach, on suspicion of operating a vehicle under the influence of an intoxicant.

The motorcycle crash occurred at 4:05 a.m., about 2,038 feet east of Kaahumanu overpass that forced the closure of all H-1 westbound lanes this morning.

Honolulu police announced the closure shortly after 4:30 a.m. this morning and reopened all H-1 westbound lanes around 7 a.m. However, traffic on Kamehameha Highway and Moanalua Road remains congested, according to the state Department of Transportation.

The 49-year-old man was riding a motorcycle westbound on the H-1 freeway at a “high rate of speed when for unknown reasons,” he drifted into the adjacent lane and collided with a vehicle driven by a 22-year-old man who allegedly was under the influence of alcohol, police said.

Following the collision, the motorcyclist was ejected onto the roadway and landed 515 feet away from the point of initial impact, police said. He was pronounced dead at the scene.

Speed and alcohol both appeared to be contributing factors in the collision, police said.

The investigation is ongoing.

This is the 24th traffic fatality this year compared to 20 at the same time last year.