The Roads Policing Unit in Letterkenny detected a couple of vehicles travelling well in excess of the 50KPH limit over the last 24 hours.
The driver of both cars were subsequently arrested on suspicion of drug driving.
One tested positive for cocaine, the other for cannabis.
“Slow down and always remain aware of the speed limit in the area in which you are travelling,” a spokesperson for Letterkenny Garda Station said.
“Never drive while under the influence of drugs/alcohol. Never take risks when it comes to safety on the roads.”