Two arrests for suspected drunken driving were made in the Culmore area of Derry on Monday night and the early hours of Tuesday.
On Monday night a Tactical Support Group patrol spotted a car being driven at speed.
The car was stopped and the driver, a 42-year-old local man, was breathalised and arrested for driving with excess alcohol.
Just over an hour later, the same patrol spotted a car being driven erratically.
It was stopped at the new Foyle Bridge and the driver, a 53-year-old man from the city, was breathalised and arrested for driving with excess alcohol.
Inspector Jonny Hunter commented: “The penalties for drinking and driving should be well known to all motorists. Those convicted by the courts face fines and disqualifications.
“Police will remain vigilant to detect these offences. It is also clear from the number of reports that we receive that people in the community want offending motorists deterred and detected.”