Earlier quoted context omitted.
Making pedestrians go out of their way to get anywhere is a great way to discourage walking and treat it as a second class citizen to driving, when it should really be the other way around. Plus, said catwalks need to be accessible, so how many elevators are you planning on putting in and maintaining now? Pedestrian bridges flat-out suck. Better to get rid of as many vehicles as possible and slow the remaining ones w…
For one. bridge you are right. Put in dozens such that you can go several km without going back down though and things are different.
If this idea were viable, someone somewhere in the world would have already done it. But the closest I can think of is Las Vegas, and that's only along one road, and it's not even a full pedestrian pathway but instead just some bridges over intersections, and those are primarily there to prevent drunks from getting run over by cars.