Colorado's traffic death toll has reached its highest point since 2004, and El Paso County is the worst of the state's 64 counties.
Officials attribute the statewide surge to impaired or distracted drivers and people not wearing seat belts.
The year's total reached 615 Monday night after a head-on Christmas crash along Interstate 70 east of Denver claimed three lives, Colorado Department of Transportation data show.
Last year, the total was 608 - the first time since 2005 that it crept above 600.
Of the deadly factors contributing to the increase, "All three of them are preventable, which is pretty tragic," said Michelle Peulen, CDOT spokeswoman.
Traffic deaths involving marijuana accounted for nearly 13 percent of the 2016 fatalities, said Sam Cole, spokesman for CDOT safety programs.
That's a steady rise since the 18 marijuana-related traffic deaths in 2013, data show.
El Paso County's high death total - 74 - isn't surprising since it's the state's biggest county, with more than 668,000 residents, the U.S. Census Bureau estimates.
Adams County was second, with 64 fatalities.
"We want to build the safest roads possible, but we can't keep people from making bad choices," Peulen said. "That's on everyone's shoulders."
State death totals didn't break 500 for six straight years, from 2009 to 2014.
The dip is partly due to the recession, when fewer people were working, driving or buying things, Cole said.
"We were surprised," he said. "We were very hopeful that the downward trend we were seeing a few years ago would continue."
Contact Ellie Mulder: 636-0198