UPDATE: Turns out it wasn't the city (or the state) that put the signs up; in any case, they've been removed .
An aggrieved Mission Hill resident reports  from Tremont Street near Huntington Avenue, which the DPW has decided people really need to know is also Rte. 9:
We can't get crosswalk signs, but please--put highway signs in the middle of the sidewalk. Perhaps we should just eliminate those pesky sidewalks all together.