Pedestrian bridges are an accessibility nightmare though, and you can't fix it with design.

Consider this: The ADA guidelines for a wheelchair accessible ramp (and your pedestrian bridge damn well better be wheelchair accessible) specify a rise over run of 1:12. In other words, for every inch of height on the ramp, there must be 12 inches, or one foot, of run. This means a 10 foot high pedestrian bridge needs 120 feet worth of ramp. That's a lot of ramp. Where do you put it? Stack it? Sure, but that adds even more distance to travel to get to the top of it. And you need it on both sides.

So now, instead of crossing 120-150 feet of road, you've got someone going up 120 or more feet of ramp, 120-150 feet of bridge, and another 120 or so feet of ramp down to cross the street. How is this better than just having cars stop at lights to let pedestrians cross?