> Your city may be similar to mine, insofar as the "residents" of the downtown area are mainly the people who work there and have already paid for parking.

If massive parking requirements is the #1 urban planning disaster of the last century, the #2 surely has to be zoning regulations that prevented mixed use areas where people can live/work/play in close proximity. And this was only to… force people to buy cars to get from place to place! Look at any city area that was developed prior to the advent of cars and they are unanimously multi-use dense areas. Cars ruined everything.

You can see this in the south bay in an incredibly acute way.

Where are Google, Microsoft, and a bunch of other enormous campuses located? East of the 101. Where are all of the residential areas? West of the 101. Gazillions of commuters need to cross the 101 to get from their home to their office twice a day. This means that everything is limited by a few small overpasses that are crazy expensive to expand.

What if people could build apartments over there? Too bad. Not zoned for housing.

My town, though much smaller, has its own "101" with similar bottlenecks. But there are now (at least) three bike bridges across it. While not free to build, they're doubtlessly much cheaper, especially since the bikes can use already existing neighborhood streets with minimal impact on the residents. I'm not sure there's a master plan for improving bike routes, but when they have to tear up a road for some reason, they usually design its replacement to accommodate bikes with dedicated lanes, bridges, tunnels, etc.

Bikes are great! 101 has at least one bike bridge. But I'd personally feel really unsafe in the bay area biking. Zero protected lanes. Tons of cars merging through bike lanes to enter turn lanes. Fast-moving roads that also have direct access from driveways.