As Street Sweeper, your job is to clean up each randomly generated neighborhood before your impossibly short shift is over, in the brief window of time when the rest of the city is asleep.
Dead leaves from trees removed long ago. Garbage, so carelessly piled. Even vomit, as big as an oil slick. The Street Sweeper takes it, and is careful not to wreck any city property in the process.
The bosses back at the station measure the yield at the end of each run, then send the Cleaner of Streets back into the next job.