November’s midterm elections added three states — Michigan, Missouri and Utah — to the growing list of 34 states that have legalized cannabis for medical and/or recreational use. That means that about 90 million Americans live where pot is legal, so the ramifications — good and bad — affect almost a third of our nation’s population.

Aside from the fact that marijuana is still classified as an illegal controlled substance by federal law — subjecting those who partake to potential criminal prosecution — the use of pot is posing a more immediate and vexing problem concerning public safety.

In a nutshell, the problem is driving under the influence of marijuana — topped by the fact that there has yet to be a reliable, efficient way to test for stoned drivers. States with the longest history of legalized marijuana for recreational use, including California, Colorado and Washington, have seen worrisome increases in weed-related traffic accidents and fatalities.

This situation has hastened widespread research into methods for roadside testing for the presence of tetrahydrocannabinol (THC), the psychoactive constituent in marijuana. Thanks to a German company, a breakthrough appears to have been made.

The first roadside screening drug test for THC — the Drager DrugTest 5000 — has been approved for Canadian law enforcement. This is a portable saliva screening system, about the size of a kitchen coffee maker, which can detect THC and other drugs as well, including cocaine. The device costs about $6,000.

The Canadian government has authorized $161 million in funding for the equipment and for police training in its use. The Drager devices are already deployed in several European countries and Australia and are undergoing testing in California, Arizona and Nevada.

To use the device, a driver/suspect is handed a mouth swab and instructed to run it around the inside of the mouth. The swab is then placed into the Drager device along with a vial of testing solution and the machine does its work. It takes about 4-6 minutes for results to print out.

There are some questions and controversy surrounding the Drager DrugTest 5000. The device’s accuracy can be affected by temperatures below 40 degrees — or if it is tilted more than ten degrees while a test is underway.

Civil rights and attorney groups are challenging the admissibility of test results in courts since there is as yet no legal threshold for the amount of THC in a person’s system when it comes to driving illegally. Alcohol cases are more black and white, with a 0.08 percent blood-alcohol level being illegal in most states.

At least two other companies — Houndlab and Cannabix Technologies — are diligently pursuing development of a marijuana breathalyzer, although neither has a device ready to move from the laboratory onto the streets for roadside use by law enforcement.