The result was that, in the summer of 1990, the A76 motorway near Heerlen became the setting for what this newspaper at the time called “a fairy tale”, one that “24 lucky recreational cannabis users could never have imagined, not even in their wildest stoned dreams”. After first being allowed to smoke a joint at the expense of the US government, they were asked to drive “a comfortable Volvo” down a motorway blocked off by the police. On top of that, they were paid a few hundred guilders. All they had to do in return was try to drive as straight as possible.
The US Department of Transportation was very interested in the results, as the effects of marijuana on driving performance had never been properly studied. At the same time, studies showed that cannabis use was common among young people in the US: reportedly, twenty-five per cent smoked weed monthly. Prosecutors didn’t have a leg to stand on in cases involving drivers who had caused accidents under the influence of marijuana.
In the US, however, sky-high insurance premiums – driven by fears of sky-high claims if anything went wrong – stood in the way of experimental studies. Dutch insurers, it seems, were less concerned, because in 1989 the US government commissioned the Maastricht Institute for Drugs, Safety and Behaviour (now the Experimental Psychopharmacology Unit), which already had several years of experience in testing the effects of drugs and alcohol on driving performance.
"Good stuff"
Nothing was left to chance. No fewer than three Dutch ministries were involved: Foreign Affairs (to liaise with the Americans), Transport and Water Management (to secure a stretch of motorway) and Justice (for an “opium permit”). Mexican marijuana, grown at the University of Mississippi, was shipped to Maastricht in a sealed container. Most participants thought it was “good stuff”, though some complained that the joints were “a bit dry”, research leader Hindrik Robbe told Observant.
Under the influence of various doses, participants made repeated runs along the empty A76 motorway. A camera mounted on the roof of the Volvo recorded every steering movement and was connected to a massive computer in the back seat, which also logged data such as speed. A driving instructor in the passenger seat was able to intervene at any moment using dual controls.
Misleading
The fact that a 22-kilometre stretch of motorway was closed on 24 separate evenings attracted considerable attention. Institute director James O’Hanlon received dozens of enquiries a day “from all sorts of people” from the Netherlands and abroad, he told Observant in September 1990. “It’s very hard to keep quiet.” In the end, he didn’t: when the analysis was still far from complete, he gave a preliminary presentation on the TV programme Veronica’s Nieuwslijn. Several newspapers subsequently reported that smoking weed had “no significant effect on driving performance” – an interpretation O’Hanlon later described as “outright misleading”.
The research team learnt from the mistake. The next series of experiments – in which participants were “let loose” in normal traffic, first on the motorway and later even in urban settings – were conducted far more discreetly. They didn’t even run advertisements for volunteers for fear of publicity. If they had, as Robbe put it in 1994 after publication of the research results, “you could have a journalist pull up beside you at any moment”.
Intervene
The findings showed that marijuana is far from harmless: the more participants had smoked, the more they swerved across the road. The combination with alcohol was “particularly dangerous”. “Someone who smokes a strong joint and drinks two beers performs as poorly as someone who has had ten beers.”
No accidents occurred during the experiments, however. The driving instructor only had to intervene twice, which Robbe attributed to drivers slipping into a dreamlike state during the monotonous drive. On one occasion, the driver had already forgotten a previous warning about a screwdriver on the road; on another, the driver missed a massive road sign entirely.
The university made smart use of the international attention the institute gained through the study, much to the frustration of O’Hanlon and Robbe. “Psychology didn’t want to involve us in the development of the curriculum, but they did want to film here for promotional purposes.”