Letterkenny Roads Policing Unit arrested a motorist who was driving in excess of a 100kph speed limit.
The driver was travelling at 138kph and then tested postitive at the roadside for cannabis.
The motorist was subsequently arrested.
Gardaí in Donegal and across the country have been checking driver’s speed as part of their National Slow Down Day enforcement operation.
They are urging people to slow down and get home safely for Christmas.
