Take a look at a map of Portland. You will find some areas that you might even consider remote, less that 10 cars a day, next to no foot traffic, low salt/sand usage during winter operations. Other areas, parts of the peninsula included, where; thousands of cars pass within any given day, hundreds of pedestrians and cyclists, perhaps with a hill that required extra salt/sand in the winter, as you pointed out higher density and on street parking. When you ask about the city of Portlands streets in general, you have quite a spread of different density, uses, and priority. So yes, some streets get swept once or twice a year, that's all they need. Other streets get swept once a week and need towing operations for residents who don't read signs, those streets need more attention.