Around ten per cent of truck drivers in the US are on drugs, according to a new report.
Random voluntary drugs tests were carried out, with the results remaining anonymous, and almost one in ten turned up positive results.
The most popular drugs were found to be marijuana and crystal meth, with three people being arrested for appearing impaired and testing positive for the illegal substance.
Police say that they tested 500 truckers, with the most common drug found being marijuana, closely followed by opiates such as heroin or Vicodin.
"It's a problem bigger than enforcement and state police," sergeant Alan Hageman told the Statesman Journal. "It needs to be looked at by the transportation community as a whole."
It isn't the first time that this kind of research has been carried out on truck drivers and similar results have appeared every time.
Truck drivers in the US are tested for drugs before they are employed and many firms carry out random tests during the year.