A 30-year-old moped rider was critically injured after he struck a curb and a sign in Kapahulu Wednesday.

The crash occurred on Diamond Head Road at about 11:45 p.m.

Honolulu police said the moped was traveling eastbound on the roadway when he lost control and struck a curb and a sign. He was thrown onto the roadway upon impact.

Police said he was not wearing a helmet at the time of the crash.

Honolulu Emergency Medical Services personnel treated the rider and took him in serious condition to a hospital. Police said his condition worsened to critical condition upon arrival at the hospital.

Alcohol and speed appear to be factors in the crash, police said. It’s unknown whether drugs were a factor.