Honolulu police are advising motorists that they will be setting up impaired-driver checkpoints before, during and after the coming Memorial Day weekend.

The checkpoints will be set up at unannounced times and locations from Friday through June 30.

Police say 21 people have been killed in 21 traffic collisions this year on Oahu. They say alcohol, speed or drugs were factors in 11 of the crashes.

Twenty-two people had been killed in 22 crashes on Oahu at this time last year.