"We just sent the guys back out there and hoped for the best and thought that perhaps the craze would die down and it never did."

At Colorado’s 420 celebrations in 2017 — weed culture’s annual high holiday — an unusual scavenger hunt took place.

Hidden around the state were 100 miniature replicas of the 420-mile marker signs that are found on six of the state’s highways.

For nearly a decade, the signs had been popular targets for sticky-fingered weed enthusiasts, for whom ‘420’ has a special meaning. Every time a sign would go missing, it wasn’t long until the replacement disappeared again. The replicas and the scavenger hunt were an attempt to send people home with a collector’s item to deter future thefts.

Sam Cole, the communications manager for traffic safety at the Colorado Department of Transportation, says the signs started to go missing around 2009, when medical marijuana dispensaries began opening across the state. Some signs, like those on the more heavily trafficked routes, were more popular targets than others, he says.

But, to the frustration of the department, they all went missing at one point or another.

The mile markers play a critical role in traffic safety, Cole says. “They are incredibly important for our first responders and traffic operations to be able to identify specifics, where crashes might have happened or weather events,” he says.

Every time a sign went missing, they would dispatch an employee to go replace it. They thought, eventually, the thefts would stop. But as Colorado moved to legalize recreational cannabis in 2014, there was another surge.

“It was getting pretty hopeless,” Cole says. “We just sent the guys back out there and hoped for the best and thought that perhaps the craze would die down and it never did.”

So they came up with Plan B: No hidden cameras or covert spy operations. Instead, they moved the signs back a hundredth of a mile and changed the number to reflect their new location: 419.99.

It’s a move other states who have encountered the issue have followed, like Washington and Idaho. Cole’s explanation for that is simple: It works.

“No one has an interest in 419 signs,” he says. “They’re safe.”

The 2017 public campaign also helped, Cole says. Each of the miniature signs came with a warning about the dangers of driving high. Those lucky enough to spot a sign in the scavenger hunt won $40 in Lyft credits and a “nice, serious chat about the importance of never driving under the influence” with traffic authorities, Cole says.

“I think it was a great way to raise awareness about an issue that’s very important to traffic safety in Colorado.”

And while the fractional signs have deterred thefts in Colorado, other states that have continued to see the 419.99 signs pilfered. The new number becoming a collector’s item in its own right.

“Well,” Cole says when this point is raised, “Maybe we need to get back up there and check on our signs.”

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