It varies street to street in in this area whether there is a limit or not on the meters. If there is, any extra coins you put in past that amount do not count. So if you get delayed for something beyond your control, you can get a ticket if your errand takes 2 minutes over the 1-hour limit, for example. There are other meters that allow up to 6 or 12 hours, and cost different amounts, it really depends on how close one is to public transportation, retail stores, etc. And there are also streets with no meters, that require permits, and those with no requirements whatsoever. It's a mixed bag, and imagine can be confusing for visitors.
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