Cannabis and Amphetamines Most Common Drugs Among Impaired Drivers

When police pull over drivers suspected of being under the influence, two substances keep showing up more than anything else — cannabis and amphetamines. A large-scale study analyzing more than 64,000 blood samples collected during traffic stops has revealed a clear pattern in drug use among drivers on Dutch roads. The research, carried out by chemists and toxicologists at the Netherlands Forensic Institute (NFI), covers a six-year window from 2017 through 2023 and offers the most detailed picture yet of drug-impaired driving since updated traffic legislation came into force.

featured-image

What the Blood Samples Revealed
Of all the samples that came back positive for narcotics, THC — the active compound in cannabis — was detected most frequently, appearing in 71 percent of cases. Amphetamines, including speed and ecstasy, came in second at 30 percent, followed by cocaine at 15 percent and GHB at 6.8 percent.

What makes the findings even more striking is the overlap between substances. One in five drivers who tested positive had not just one drug in their system but a combination of two, three, or even four. The most common pairings were THC with amphetamine or cocaine, and GHB with amphetamine — a concerning trend that points to a broader risk on the roads than single-substance use alone.

The profile of the typical drug-driving suspect is also telling. Nearly all — 92 percent — were male, with an average age of 29. Two out of every three drivers tested returned a positive result. Younger drivers under 26 were more likely to have THC in their blood, while cocaine and amphetamine use became more common with age.

A Law That Changed Everything
The legal backdrop to this research matters. On July 1, 2017, an updated Road Traffic Act took effect in the Netherlands, introducing something the previous 1994 law had never included — defined threshold values for drug concentrations in the blood. Before that change, the law simply prohibited driving after taking drugs, without specifying how much was too much.

With the new rules came a new enforcement tool: a roadside saliva test that police can use when drug use is suspected. If the test flags a concern, a blood sample is taken and sent to an accredited toxicology laboratory, where specialists determine exactly which substances are present and whether they exceed the legal limits. This NFI study is the first comprehensive overview of drug-driving data gathered under that updated framework, and follow-up research focusing specifically on drug-related accidents is already in the pipeline.