Gate all the alley ways that are no longer in use (formally used for garabage pick up). This helps to cut down on graffiti on the fences, people driving in them and using them to do drugs or other illicit activites, cuts down on foot traffic as well and people using the alley as a dumping ground.
There are programs out there for this idea, I have seen in it in use in my neighborhood. Would be great to have this city wide.