It looks quiet, safe, inviting, a good place to stroll with your significant other. Well, it is and it isn't. Do you see the patched sidewalk concrete? The patches are there because the sidewalk heaves in the spring as the spring thaw arrives. And the heaved sidewalk can catch a foot, causing the walker to fall, and to fall hard on solid concrete.
The city knows of the danger and regularly grinds down the ridges. But each winter the sidewalk heaves again. Eventually the city rips out the damaged concrete and replaces it with a new, fresh, smooth sidewalk. Tripping threat eliminated, at least temporarily.
One is left to wonder why, in a city with relatively mild winters, this problem is so common. Does the city put in sidewalks on the cheap, scrimping on the a deep, solid foundation on which the concrete surface sits?