CHICAGO — A foundation that opposes the legalization of marijuana and other drugs is warning drivers about driving while impaired by drugs as people prepare for New Year’s Eve celebrations.

The Drug Free America Foundation has offices in Chicago and Florida. It says in a statement this week that the problem is on the rise even as many still think of impaired driving as an alcohol-related issue.

Illinois law enforcement has begun acknowledging the challenge. Police in Carol Stream announced this month they’ll soon start trying new mobile tests to detect if drivers have drugs in their systems and which ones.

The foundation’s executive director, Calvina Fay, says statistics show more people are driving impaired by drugs. She argues it’s especially evident in states that liberalized marijuana laws, such as Colorado.