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In the years since marijuana was legalized in four states out west, car crashes in those states rose faster than those in neighboring states that haven't legalized weed.

Two new studies released Thursday show that both police-reported car crashes and accident-related insurance claims jumped in Colorado, Nevada, Oregon and Washington after marijuana legalization. Those four states were compared with their neighbors Idaho, Montana, Utah and Wyoming, which all still prohibit marijuana.

The studies were done by the Insurance Institute of Highway Safety and the Highway Loss Data Institute, and found that police-reported car crashes rose 5.2 percent and insurance claims for car accidents rose 6 percent in those four legal states, respectively.

The studies raise as many questions as they answer as New Jersey moves closer to a vote on legalization, experts say.

Many people in New Jersey have questioned whether legal weed would make the state's dense network of roads less safe, as lawmakers continue debating legalization.

Despite showing an increase in crashes after legalization, the studies were unable to show that the presence of legal marijuana was a factor in the jump in accidents.

"We can't directly conclude cause and effect here," said Russ Rader, spokesman for the IIHS and HLDI, which conducted the studies. "We don't know how many drivers in crashes in these states actually consumed (marijuana)."

Jolene Forman, a staff attorney at the Drug Policy Alliance, said, "this report doesn't really tell us anything about marijuana."

But the president of the IIHS and HLDI said that states legalizing marijuana appears to make roads more dangerous.

"The new IIHS-HLDI research on marijuana and crashes indicates that legalizing marijuana for all uses is having a negative impact on the safety of our roads," said David Harkey. "States exploring legalizing marijuana should consider this effect on highway safety."

NJ Advance Media reported earlier this year that there is currently no legal limit for driving under the influence of marijuana, and there is also no widely accepted roadside test to detect marijuana usage. These two factors that make detecting people driving under the influence of marijuana more difficult than with alcohol.

Several companies in the U.S. are working to develop a breathalyzer to measure marijuana, but there isn't one that's been widely adopted by law enforcement. Without a reliable test, New Jersey would have to expand its force of drug recognition experts should the state legalize weed.

Drug recognition experts are police officers specially trained to spot impaired drivers. New Jersey already has a stable of these officers, with only California having more.

But, should marijuana become legal, Christopher Didzik, president of the New Jersey Association of Drug Recognition Experts, earlier this year said the state will need more of the officers.



"Our main concern is what we're going to do to prevent impaired driving," Didzik said.

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Payton Guion may be reached at PGuion@njadvancemedia.com. Follow him on Twitter @PaytonGuion. Find NJ.com on Facebook.