Wisconsin

Solutions are what's needed, not repeating the obvious point that there is a problem.
The UK uses a tongue swipe kit to test for several illegal drugs; cocaine, marijuana and opiates.
The US doesn't use any drug testing standard, and I don't think Wisconsin does this at all?
They take suspects to a hospital for a blood test, which is a very expensive and time consuming process.
"...drug tests are not run if the blood alcohol concentration (BAC) is above 0.1 g/100mL unless there is a Drug Recognition Expert evaluation or a crash. Tests also stop once a restricted controlled substance (cocaine, methamphetamine or delta-9-THC, LSD, PCP, hallucinogens, narcotics, etc.) is detected and that substance is reported. "

A road side drug test is the smartest thing to add to reducing DUI incidents. Training cops for drugs, compared to a test kit, should come only after road side test kits show a high failure rate. But we don't even try this low cost option.

Impaired driving has always existed, since the 1920's federal drug laws were created. Solutions are rarely presented, either from the law enforcement perspective or the suspects behaviors.

There is also a great number of drivers who are 'impaired' with OTC drugs, like antihistamines (drowsy), the many 'maintenance' drugs for cardiac, hormonal and infection control. These legit drugs do reduce awareness and come with warnings on the info provided by pharmacies.

Additionally, technology can easily prevent a car being used if the driver is impaired. Sensors can smell alcohol or aromas, and test skin indicators. The costs are minimal, compared to the average $30,000 new car cost.

With millions of cars and tens of thousands dead every year from DUI, the police seem to be adverse to what tech can provide, over the judgement of the individually trained 'objective' attitude of each police officer.
I would prefer using science to reduce DUI's, as every training-only attempt has not reduced DUI by any significant amount.