Today I'd like to point you towards an article from Sidsel Overgaard of NPR concerning a policy you'll only see in the most socially liberal of locations, such as your Amsterdams, your Vancouvers, your Sydneys, scattered locations around Europe, and in the article's case, Copenhagen. It's called a drug consumption room, or DCR- Copenhagen calls them 'fix rooms'. (The first DCR to be officially sanctioned, for the record, was in Bern, Switzerland, in 1986.)
The theory behind a DCR is this: a user of your harder drugs, even if they don't want to be on the drug and want to quit, are nonetheless usually not exactly able to stop taking it without at least some form of assistance or support. So trying to hunt them down and arrest them when they have to respond to that addiction isn't really going to get them any closer to quitting, and besides, chasing them down only serves to drive them deep into the city's nooks and crannies, making those nooks and crannies more dangerous for everyone else. A DCR is a place where a user with an addiction can openly come, anonymously through a nickname, and take care of that addiction in a safe place, using sterile equipment, under the supervision of a nurse, without fear of arrest or public humiliation. While they're there, if they do express an interest in quitting, resources to start along that path are placed within easy reach.
Copenhagen has a 2-square-mile zone around at least one of their two DCR's where drug use does not make you a candidate for arrest; police will instead try to point you in the DCR's direction. (Dealing drugs, meanwhile, will still get you arrested.) They've had the DCR program in place for about a year, and while it hasn't completely taken drug use off the streets, you could be forgiven for thinking so, as one region of town formerly rife with users, needles and drug paraphernalia has been made nearly clean through users going to the DCR instead. They also report that, while there have been overdoses along the way, so far, nobody has died from one, at least not in Copenhagen.
Meanwhile, a study published in 2006 in the New England Journal of Medicine, using Vancouver's DCR as a test subject, showed increased enrollment in detox programs among users of the facility. There are a couple possible reasons for that: the program is within the easiest possible reach; lessened fear of punishment for having the drugs on them in the first place; a buildup of trust of the authorities through continued positive interaction with them; and as one Copenhagen user in the NPR article notes, being at the DCR allows users to be amongst people that they can be social with on whatever level, be it authority or fellow user, and just being social at all- as opposed to being alone in some alley somewhere- helps show users some sort of light at the end of the tunnel.
Despite that evidence, let's not get too ahead of ourselves. This is very much the kind of thing that's only going to grow on a city-by-city basis, because asking cities to open a facility where people can legally take drugs, even for a reason and goal as that, is a lot to ask someone to wrap their head around. Any city that adds a DCR is not going to be cajoled into it; they're going to need to see proof to their individual satisfaction that the concept works, because otherwise the worry is going to be that you're just allowing people to shoot up unencumbered and so people are going to start using more often, thus making their problems worse. Which despite the evidence so far is not an easily-dismissed argument, and in some cities, maybe those fears even get realized, especially if a city runs their DCR poorly or halfheartedly and/or fails to gain the trust of their local users. Copenhagen has buy-in from their local police, and they work to make it function properly, but in some of your harder-line locations, where police are more collectively inclined to punish, trust would be a much rarer commodity. Joe Arpaio, the self-styled 'America's Toughest Sheriff', could never put one in Phoenix, to use an extreme example. He'd have no credibility. The users there would likely dismiss it as a sting operation, and the way some of the authorities there would run it, there's a possibility they'd be right.
All you can really say is, any city that adopts the practice, you need to commit to it wholeheartedly and sincerely. And best of luck to you.