An army of officers will fan out over Memorial Day weekend around the country with DUI checkpoints and patrols aimed at snagging not just drunk drivers, but the growing menace of drugged drivers. This intensified focus comes on the heels of a new study that finds an increase in fatal accidents involving marijuana since Colorado legalized medicinal marijuana. The University of Colorado school of psychiatry researchers found that 4.5 percent of traffic fatalities involved pot prior to medicinal marijuana legalization, while the number more than doubled, to 10 percent, by 2011, after medicinal marijuana was widely available. But drugged driving -- DUID -- is being recognized as a rising threat. \u201cWe've spent the last 30 years fighting drinking and driving and now we're realizing that we need to continue that fight but add drugging and driving to it,\u201d Chris Cochran, spokesman for the California Office of Traffic Safety (OTS), said Wednesday. \u201cIt just hasn't been in front of the public the same way that alcohol has." That\u2019s beginning to change. A University of Colorado study released May 15 found what it termed a \u201cdramatic increase\u201d in the state\u2019s number of fatalities that involved a driver under the influence of marijuana. The research was commissioned to look at whether the legalization of the medicinal use of marijuana since mid-2009 had led to more roadway deaths. More Drivers Using Marijuana Researchers at the campus outside Denver compared Colorado roadway fatalities with those of the 34 \u201cnon-medical marijuana states,\u201d or NMMS. Colorado voters legalized marijuana for medicinal use effective mid-2009, which is when it \u201cbecame commercially available and prevalent,\u201d the authors wrote. The research counted the state\u2019s weed-related road deaths compared to states where medical pot was not legalized. Those states had no increase in marijuana-involved traffic fatalities. The rate of fatalities involving alcohol was unchanged in Colorado and the other states. The research did not link the cause of the crashes to marijuana impairment; it only noted when at least one of the drivers had cannabis in his or her system. Colorado voters have since legalized the recreational use of marijuana, which went into effect Jan. 1, but ties to accident rates have not yet been examined. \u201cPrevention efforts and policy changes in Colorado are needed to address this concerning trend in marijuana-positive drivers,\u201d concluded the research team. \u201cIn addition, education on the risks of marijuana-positive driving needs to be implemented.\u201d For now, the traditional DUI checkpoint is still found to be a cost-effective way to deter impaired driving or catch it while it\u2019s underway. Earlier this month, during the weekend preceding May 5, nearly 500 drivers were arrested in Los Angeles County for driving under the influence during Cinco de Mayo celebrations. Yet according to a first-time California report, drugged driving has eclipsed drunk driving: more drivers were found to be driving drugged (14 percent) than were driving drunk (7.3 percent). The roadside survey conducted by the state OTS, which came out in November 2012, found other startling results: drugs that would affect driving were found in one of seven weekend night drivers in California. Surprisingly, 1,300 drivers in nine California cities agreed at roadside spots to submit breath or saliva samples, or both. The drivers were stopped during the hours of highest impaired driving -- from 10 p.m. to 3 a.m. on Fridays and Saturdays. Details were not offered about why hundreds of drivers would voluntarily provide potentially damning physical evidence. Alcohol impairment was assessed with breath samples while saliva samples were examined for signs of THC (marijuana\u2019s active ingredient); other illegal drugs; prescription, and over-the-counter medicines that can affect driving. Of the drivers who tested positive for drugs, marijuana was most common (7.4 percent), still slightly more than alcohol. Drivers Using Multiple Drugs Other survey findings: Of the 7.3 percent of drivers who tested positive for alcohol, 23 percent also tested positive for at least one other drug. \u201cThis combination can increase the effect of both substances,\u201d the survey report noted. Illegal drugs were found in the systems of 4.6 percent of drivers. An equal amount also tested positive for legally-prescribed or over-the-counter medicines known to impair driving. More than one in four drivers (26.5 percent) who tested positive for weed also tested positive for at least one other drug. Using other data, the National Highway Traffic Safety Administration -- which grants and funds DUI checkpoints throughout the U.S.\u00a0 -- has previously reported that among drivers killed in California road crashes in 2010, 30 percent tested positive for legal or illegal drugs. \u201cThese results,\u201d said Christopher J. Murphy, director of the Office of Traffic Safety, \u201creinforce our belief that driving after consuming potentially impairing drugs is a serious and growing problem.\u201d An estimated 5,000 California Highway Patrol officers will be dedicated to impaired driving over the Memorial Day weekend that stretches from Friday through Monday, the state OTS\u2019s Cochran said. Thousands around the country will be doing the same patrols. Locally, hundreds of additional checkpoints will be staged. Every $1 invested in such preemptive measures saves $6 in the long run, the National Highway Traffic Safety Administration reports. In L.A. County alone, one of the most populated and visited regions in the U.S., officers will swarm local highways Friday through Monday. Law enforcement urges Memorial Day holiday revelers to follow these five tips: \tPlan ahead. Before the party starts, line up rides home for your group of friends or family, and yourself.\u00a0Options include a reliably sober friend; a designated sober driver, a cab or perhaps a tipsy tow service. \tAct responsibly if you\u2019re hosting the party. Don\u2019t be afraid to limit or monitor the number of drinks you\u2019re serving each person. \tOffer free "mocktails" for your personal designated sober driver or those at your party. \tIf you are the designated driver, download the smartphone app that helps you find locations near you for free non-alcoholic drinks and other freebies -- www.ddvipca.com \tDon\u2019t hesitate or worry about bothering police. Call 9-1-1 if you see weaving or other dangerous driving.