Police from Portadown's Mahon Road RPU have been on patrol along the M1 from early morning.
At Noon today they arrested one driver in Glenavy after a breath test showed they were 3 times the limit.
Earlier police said crews from Mahon Road RPU were on the motorway carrying out breath tests as part of the PSNI's anti-drink driving campaign.
Writing on Facebook they said: "Twelve drivers were found to have consumed some alcohol but were under the legal limit.
"One driver was over the limit, and arrested."
