There were 1,230 cases of people driving with at least two drugs in their system last year.
Over 140 involved a combination of cannabis, cocaine and benzodiazapines, with all three substances found in these samples.
The Medical Bureau of Road Safety says 'polydrug use' was commonly detected in 2021.
Sinn Féin's transport spokesman, Darren O'Rourke, says it's a cause of serious concern.
