Police will start manning holiday impaired driver checkpoints on Friday at unannounced times and locations in an attempt to reduce traffic injuries and deaths.

The DUI checkpoints will be operated through Dec. 31, New Year’s Eve.

As of Monday, 49 people have been killed in traffic collisions on Oahu. Speed, alcohol and/or drugs were factors in 15 of those crashes. Fifty-one people were killed in traffic collisions during the same period in 2012.

The legal drinking age is 21. Promoting intoxicating liquor to a person under the age of 21 is a misdemeanor punishable by up to one year imprisonment.