This was the issue with the "Millenium" bridge in London, renamed unofficially as the "wobbly" bridge. Because of the nature of it's construction people would

This was the issue with the "Millenium" bridge in London, renamed unofficially as the "wobbly" bridge. Because of the nature of it's construction people would over time start to sync their steps, the more this happened the more the bridge swayed and the more people synced their steps. It was fixed by adding dampers. https://en.wikipedia.org/wiki/Millennium_Bridge,_London https://en.wikipedia.org/wiki/Millennium_Bridge,_London