Elevated pedestrian catwalks are a recurring architectural fad. They don't tend to work out very well outside of a few specific areas, though, as pedestrians traffic is most popular in situations where pedestrians also have access to lots of street-level homes and businesses.

Consider further coverage and commentary such as

https://www.academyofurbanism.org.uk/streets-in-the-sky-the-...

https://failedarchitecture.com/the-downfall-of-londons-stree...

https://www.architectural-review.com/essays/campaigns/notopi...