[micromacrofoot]

It's not really a solution, because even then no one's perfect about using them, but it can help. Rats will chew right through a plastic trash can if they're desperate, and steel dumpsters eventually rust out and create nice little rat doors.

Almost ever major city has some level of rat problem, with underground transit and other man-made tunnels I believe the problem is essentially impossible to solve. It's all about management.