The NRP stopped about 600 vehicles during R.I.D.E. programs in St. Catharines and Port Colborne.
Officers administered 26 roadside screening tests on Monday and four drivers found themselves in the warning range.
They each face a three-day licence suspension.
The officers also issued tickets for traffic related offences.
Boy Severely Hurt in Lundy's Collision
Hamilton police helped the NRP arrest a driver for impaired driving
Fed/Prov Volunteers Help Cleanup
City of St. Catharines says Team Rubicon volunteers are assessing damage
Police Investigating Fatal Wainfleet Crash
They say a motorcycle driver lost control on Golf Course Road in Wainfleet
Man Arrested in Relation to Child Porn
Police say Port Colborne man didn't comply with release order, he's been active in online tutor program
Independent Group to Review Flooding
Mayor Mat Siscoe says the city covers infrastructure extensively
Youths Charged in Niagara Bank Robberies
Police say there were plans for a 4th robbery, organized by Toronto youths
4 Suspects Wanted After Assaults
Police say one man assaulted twice
Motorcycle Rider Crashes on River Street
Police say the driver suffered life threatening injuries, looking for witnesses