Illinois Cops want to know who’s driving while stoned. Tests are being developed, but level of impairment after smoking weed is still hard to measure.

When marijuana sales become legal in Illinois next year, it will remain illegal to drive while high. But police say they still won’t have the tools to enforce laws against stoned driving the way they’d like.

Law enforcement officials expect a significant increase in the number of people driving after smoking pot. While patrol officers can use Breathalyzers to help check whether people are driving while drunk, they have no approved roadside test to see whether drivers are stoned. Police in Carol Stream are hoping to help change that.