Motorists were monitored for both drugs and alcohol at checkpoints in Donegal, Monaghan and Cavan over the weekend in a unique Garda twin crackdown.
In the first Irish operation of its kind, buses carrying revellers to and from nightclubs were also checked. Sniffer dogs and their handlers from the Garda drugs unit in Dublin were dispatched to work alongside local traffic corps officers.
On Friday, the first night of the operation in Monaghan and Cavan, four arrests were made for a combination of drink-driving and drugs offences.
In Donegal checkpoints were set up in Inishowen and in the Letterkenny-Lifford area.
Murphy, one of only six drugs-detection dogs in the State, and a veteran of Dublin drugs busts with detections worth €60 million sniffed out during his career, was on his first roadside checkpoint operation.
His handler, Paul Conway, said the dog was more familiar searching suspect city homes. Four of the State's six drugs-detection dogs are based in Dublin. The others are in Cork and Limerick.
How successful the operations were won't be known until today, when the weekend figures are tallied.
The drugs/drink checks follow claims by road safety and anti-drugs campaigners of inadequate measures to detect and prosecute motorists who are under the influence of drugs.
Gardaí have complained they lack powers to test somebody for drugs at the roadside in the same way as they can conduct random drink-driving tests.
If drugs were detected during the weekend, prosecutions will be for possession of narcotics. Drug-driving prosecutions may depend on whether illicit substances showed in blood or urine samples.
Supt John McFadden, Garda northwest regional traffic chief, ordered the twin crackdown. He said the importation of the sniffer dogs from Dublin meant gardaí were using whatever resources were available in the battle against drugs. He pledged there would be more unannounced joint drink-drive and drugs operations in the region.
Well-known Donegal anti-drugs campaigner PJ Blake welcomed the move but claimed that while drugs carriers may be exposed, there would be little noticeable impact on drugs-driving until gardaí have powers of roadside eye-pupil tests similar to those available to police in other jurisdictions.