And I want to ask: why? When you walk under a bridge, you're avoiding what is on there, whether it be vehicular traffic or rails. How is this bad?
The question even extends to highways: in Houston, there's the Pierce Elevated, a highway that critics say "cuts" through the area between Midtown and Downtown, but that's a bit of a misnomer since the Midtown area didn't really exist until after the Pierce Elevated and the 59. You can even see when the Pierce Elevated was built (page 15 of the PDF) the area didn't look at all as it does now. The Pierce Elevated isn't in bad shape (it had an extensive re-do in the late 1990s) but it is congested. A lot of people think that it would be better without an elevated highway and replaced with a street-level boulevard. The prototype for this is a few examples in San Francisco, which replaced a few highways with boulevards as with another example in Milwaukee. However, Keep Houston Houston candidly reminds us that freeway removals are only done when it was a spur that was rendered more or less useless after the rest of the plans were cancelled, or that it was rendered obsolete with a wider freeway anyway. The Pierce is neither of these and is mostly congested because of outdated exits and entrances, including a particularly short left-hand entrance into the freeway from eastbound Allen Parkway.
There's no real rhyme or reason why the Pierce should be dismantled, but boulevards, favored by the anti-freeway crowd, make even less sense. Here you have a three to four lane road to cross, then going under the freeway, whereas a boulevard option would have you crossing on foot 9-10 lanes of traffic. Crossing streets tends to suck, and in most options if available, I'll take an underpass and go under a bridge.
We're not here to talk about the Pierce Elevated, but what is it about elevated structures that people hate?