A driver allegedly tested positive for cocaine after they were caught more than doubling the speed limit.
The motorist in Co Mayo was clocked traveling at 204km/h shortly after midnight on Wednesday.
Gardai from the Mayo Roads Policing pulled over the driver who failed a roadside drug test.
The motorist was subsequently arrested and their vehicle was seized.
A spokesman said: "Mayo Roads Policing detected a car driving at 204km/h in a 100km/h zone on the N5 after midnight on Wed May 13.
"Gardaí stopped the car. Driver tested positive for cocaine on a roads side drug test.
"Driver arrested, and vehicle seized. File is being prepared for the DPP."