For a second day in row, Niagara police carried out RIDE checks at two locations in St Catharines.
They stopped about 600 drivers.
Twenty-one were required to give breath samples, but none of them resgistered a 'fail' on the breathalyzer.
Three drivers did have their license suspended for three days.
During National Impaired Driving Enforcement Day, the Niagara Regional Police arrested and charged five drivers with impaired driving related offences, including five drivers who were issued three day licence suspensions.