LANCASTER, Penn. – Drug users and others looking for isolated space for illegal activities have long favored public restrooms, and naturally business owners have tried ways to deter such activity on their premises—both for the sake of customers and employees, the Washington Post reports.

At least two convenience store chains are experimenting with blue lighting in restrooms to make it more difficult for drug users to shoot up. Six months ago, Turkey Hill Minit Markets put blue lights in the bathrooms at 20 of its more than 260 stores to test whether the colored lights would lower incidents of drug use.

“With the problem across the nation with drug use, we were looking for something to get that activity off our properties,” said Matt Dorgan, division asset protection manager for Turkey Hill. He noted that the lighting has corresponded with a “dramatic reduction” in drug incidents.

In 2017, Sheetz added blue lighting to bathrooms at a store in West Virginia and Pennsylvania. While the chain hasn’t completed its test, spokesman Nick Ruffner said “we've seen steps in the right direction” because of the lighting change.

As security experts note, these retailers are attempting to balance customers need for clean and accessible restrooms while discouraging illegal—and unsafe—activity on its property. Having employees regularly check public restrooms is one of the best deterrents to crime overall.