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DENVER — According to a new study by the Rocky Mountain High Intensity Drug Trafficking Area, marijuana-related crashes have jumped 15% since Colorado legalized recreational pot, and all traffic deaths have increased 31% in that time.

“It took us a long time to get people to understand drinking and driving is a dangerous thing,” said Colorado State Patrol Master Trooper Gary Cutler. “We need to get people to understand that it’s the same way with marijuana.”

In 2013, the study says 11% of drivers involved in fatal crashes tested positive for marijuana. Over the past three years, that number has risen to about 20%.

On Christmas Eve 2018, Brett Shaw’s wife Sancy and his daughter Charlee were involved in a serious crash on Interstate 70 west of Denver. An impaired driver drove across the median and hit the Shaws’ vehicle head-on. Sancy and the driver of the other vehicle were killed. Charlee was seriously injured.

“Sometimes, she’ll kind of touch the side of her face where her scars are and she’ll say ‘accident,’” Shaw said of Charlee.

CSP says the driver of the other car had alcohol and marijuana in their system. And while Shaw says Charlee is getting back to jumping on trampolines and hiking with her father and brothers, it’s hard to ignore who is missing.

“Someone’s lack of responsibility and their actions over the course of one evening can devastate someone else’s life — someone else’s family’s lives — forever,” Shaw said.

CSP says they’re able to tell if someone is under the influence fairly easily, but the challenge is when drivers are using more than one substance.

“Are they mixing it with alcohol?” Cutler said. “Are they mixing it with another drug? And so that’s what our interviews on the side of the road are meant to do.”

According to the study, in 2018, 75% if drivers who tested positive for marijuana also had alcohol, other drugs, or a combination of both in their system.