Typical pedestrian bridges aren't 150 feet wide, though. Nor do most have grass growing on them (at least, not intentionally). This is, in fact, a fairly unusual infrastructure project.
Pedestrians also happen to be much denser than cars though, since cars are mostly air, while humans are mostly water, which can lead to some interesting situations (and Wikipedia articles)
My dad worked for a while as an accident investigator for the Air Force. One time there was a crash where a pilot deliberately flew into a cliff at top speed.
The only evidence they ever found of his body was a finger joint. My dad said the body just turns into spray at those speeds.
