The concept of such a shared space is not entirely ridiculous. You’ll find them all over the Netherlands

The dashed lines to the side help optically narrow the road, and the lack of a median line helps make drivers feel less at ease.
This is supposed to help lower speeds. And it also helps to indicate to drivers that cars are not the only important mode on this road.

However it’s not just the bike lanes that are the key to these kinds of streets being safe, it’s all the traffic calming around it as well.
A street like this is only successful if the number of cars is relatively low, and the cars that do drive there don’t go much faster than the cyclists.