Anti-marijuana advocates predicted a whole lot of pain would befall Colorado if it legalized marijuana. One of the most persistent bugaboos was the potential roadside carnage that could occur as a result of drugged driving. That's why, 11 days after Colorado stores began to sell legal marijuana for the first time in a century, it made national news when a 23-year-old man named Keith Kilbey crashed his pickup truck into a row of police cars with emergency lights flashing on a highway east of Denver.

Before he could be tested to determine which substances were coursing through his bloodstream, a spokesperson for the Colorado State Patrol announced that Kilbey had been charged with driving under the influence of drugs. "We believe marijuana," she said.

A stoned driver smashing into two brightly lit, motionless cop cars seemed to confirm the prophecies made by anti-pot Cassandras. But earlier this week, after Kilbey accepted a plea deal to avoid jail time, the district attorney revealed that although Kilbey was high, he was also plastered, with a blood alcohol content of .268, more than three times the legal limit. (For context, this is more than twice as drunk as Mel Gibson was in 2006 when he went on an anti-semitic tirade and called a police officer "sugar tits.") Previous police statements had omitted the fact that Kilbey was inebriated, although, as Washington Post blogger Radley Balko points out, it would have been virtually impossible for the cops on the scene not to notice that he was falling-down drunk.

For Balko, the revelation that Kilbey was cross-faded makes Colorado's police, the main sources for recent reports that the state's great pot experiment has gone awry, that much more unreliable.

But the episode also highlights one of the most critical elements of the drugged driving debate, which has so far gone largely ignored. Forget the woman who drives home from a bar after one too many beers or the guy who smokes a joint and gets in his car for a hoagie. It's the combination of the two that should concern us most. Mixing alcohol and pot makes for the most dangerous motorist.

Mark Kleiman, a leading drug policy analyst, writes on his blog that "anyone who tests positive for cannabis on a mouth swab (which detects use within the past few hours) should be considered guilty of impaired driving if that person's BAC is detectably different from zero." That's because drinking a couple PBRs after smoking some pot — not to mention the high-concentration edibles that rendered Maureen Dowd speechless for eight hours — makes for a more dangerous driver than a tipsy high-schooler. A study conducted in 2013 found that the odds of a fatal crash were twice as high for a drugged driver compared to a sober driver; the odds were 14 times as high for drunk drivers, and a whopping 23 times higher for motorists who had both drugs and alcohol in their system.

This might have been less of a concern before pot was legal, when smoking in the comfort of one's home was pretty much the only option. But now, Colorado's weed entrepreneurs are producing a dazzling array of alternatives — including vaporizer pens, an unobtrusive, odorless marijuana e-cigarette loaded with a powerful pot extraction. The innocuous pens can go anywhere an e-cigarette goes, with minimal risk of discovery. What's to stop people from smoking them in bars?

Despite this danger, the state of Colorado's concerns remain firmly centered on driving high. Colorado's recent public awareness campaign about drugged driving stars goofy stoners who realize as they're lighting up their grill that they've forgotten to buy fuel. (Tagline: "Grilling high is now legal. Driving to buy the propane you forgot isn't.)

Anxieties about pot-addled drivers may have something to do with the disturbing normalcy of drunk driving, which accounts for one-third of traffic-related deaths in the U.S. It's much easier to pontificate about stoners on the road than to change the legal BAC limit for motorists, which marijuana researchers say would curb most of the ill effects of driving while high. The lack of attention to the potentially fatal combination of pot, alcohol, and a steering wheel shows an alarming lack of foresight. Kilbey's accident can't tell us anything definitive about whether marijuana is safe or dangerous. But it should be a reminder that having one too many beers and then smoking a joint is a terrible idea — especially if you need to drive home.