More meth and MDMA was uncovered in the first six months of roadside drug testing than cannabis, according to new reports.

Police data shows just over three percent of saliva tests came back positive, out of more than 4,000 conducted by officers.

The Spinoff reports in nine of the 13 police districts, meth and MDMA was detected as frequently or more frequently in drivers than cannabis.

Drug Detection Agency head Glenn Dobson says that's higher than expected.

"Meth was increasing from a workplace drug testing perspective - and that creates some huge safety problems, both on the road and in the workplace, but we normally see cannabis at a higher rate." 

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