In response to the drug overdose crisis, a number of U.S. cities have considered opening safe injection sites for drug users. At these sites, addicts can use drugs supervised by trained professionals who can make sure they're using clean needles, offer recovery counseling and provide potentially lifesaving medical help in the case of an overdose. There are currently no formal safe injection sites in the U.S., but the push to establish them cleared a major legal hurdle last week when a judge ruled a proposed site in Philadelphia would not violate federal law. Other major cities such as Boston, Seattle, San Francisco and New York have considered opening their own locations. Safe injection sites exist in at least 10 countries, with Canada having more than 40 locations.