Ok, I get it now; proposal B (Ann Arbor 2020) has a context. Historically, the city has built new sidewalks by charging adjacent property owners.
If proposal B passes, the city will have a few years during which it can add new sidewalks with tax revenue instead, and it's part of the city's efforts to discourage driving and encourage walking.
As a citizen who walks everywhere and almost never drives, I am in favor.
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