Police say a driver impaired by marijuana caused a July 14 Bay Area crash that injured California state Controller Betty Yee – the latest incident to illustrate the absolute need for tests that can reliably detect marijuana intoxication. In the era of legal recreational pot use in California, Maine and seven other states, it’s crucial to public safety.

Several methods have already been developed. Among them are the Drager DrugTest 5000 machines owned by San Diego police, which use oral swabs to confirm the presence of drugs in the body, with positive results leading to follow-up blood tests. Chief David Nisleit recently told the San Diego Union-Tribune Editorial Board that he believed it was effective when combined with officers’ observations of drivers suspected of impairment. Canada also recently chose the Drager machines for national use.

But Drager also has plenty of skeptics. The Truth About Cars website noted Friday that some authorities in Australia and Ireland have lost faith in the devices’ accuracy and reliability. Last year, an Orange County (California) District Attorney’s Office official voiced similar concerns, citing unacceptably high numbers of false test results.

Here’s hoping the UC San Diego Center for Medicinal Cannabis Research finds a better way. It’s been tasked by the Legislature to come up with a reliable roadside test for marijuana impairment. Such a breakthrough would make the world a safer place.