Drugs and driving: Impaired but not busted?

ORLANDO, Fla. – A 2016 study found that 44 percent of drivers killed in crashes tested positive for drugs, and 16 percent had opioids in their system. 

Different drugs have different effects on drivers, so it's difficult to standardize tests and limits. 

The headlines are a constant reminder of the opioid epidemic in the United States. 

"We're also seeing some statistics that come out that are somewhat alarming -- especially with the opioid crisis. And some of these other drugs that are on the market and more people are dying from drug overdose than handguns in this country," said Patrick Bordnick, dean at Tulane University School of Social Work.

According to the National Institutes of Health, up to 29 percent of patients prescribed opioids misuse them. 

But what happens when someone on opioids gets behind the wheel? 

A study out of Norway tested two common opioids in an on-road driving study. 

When participants took a single dose, their impairment was mild, and when the opioids were taken at their highest dose, participants had increased sleepiness and poor cognitive task performance. 

Four participants even had to stop the driving test because they were falling asleep. 

Doctors and patients should have a conversation about dosage, driving and alternatives.

"If you have a problem or have had past dependency problems on substances, being able to talk with your doctor about alternative treatments," Bordnick said. 

Unlike a breathalyzer to test for alcohol, there is no standard roadside test for drugs. 

Many states like Nebraska rely on specially trained law enforcement officers called drug recognition experts. 

Others are testing a mouth swab called the Dräger drug-test 5000 that can identify THC, cocaine, opiates and more.