Correlation between marijuana use and accidents questioned by police

COLORADO (CBS) -- Safety advocates claim that car crashes are occurring more frequently in states where marijuana use is legal. But those on the ground - including law enforcement- say that's not entirely true.

Colorado led the nation with the first sales of legal recreational marijuana in 2014. But the drug's impact on roadway crashes has not been well documented.

Thursday, the highway loss data institute reported an increase in insurance claims filed for collisions in Colorado, Washington, and Oregon -- three states where recreational marijuana is legal.

But those numbers do not match what the Colorado state patrol has tracked. Sargent Rob Madden said the agency has actually seen a decrease in the number of driving impaired accidents since pot sales became legal.

There have been tragedies from mixing marijuana and driving. Last year high school student Chad Britton was killed by a teen driver high on pot.

And while pot may be legal, impaired driving is not, even when it's that much harder to detect.