This generally works were the traffic is low, in sub urbs and on specific paths(not sidewalks in metropolitan areas). combined pedestrian walk and bicycle paths are possible, in sub urbs and in more rural areas, though even there they should generally be split and only used for overtaking:

https://www.osteraker.se/images/18.5bb0400617c11d33b551007/1...

In bigger cities where the foot traffic is high, it's absolutely not possible, in my opinion.