No, I'm serious: has any city in the US ever had traffic at some (bad) level, implemented some set of new policies, then had traffic drop substantially while maintaining the same population density (i.e. I won't count the abandonment of Detroit.) I certainly don't know of any, which makes me doubtful about anyone's proposals to fix traffic.
This was accomplished by: 1. Never building a freeway and never expanding any road capacity at all. (This is a strong disincentive to drive to downtown) 2. Building rapid transit. 3. Building residential housing in and adjacent to downtown so that people can just walk to work.
http://www.jtc.sala.ubc.ca/newsroom/patrick_condon_primer.pd...
https://en.wikipedia.org/wiki/The_Death_and_Life_of_Great_Am...
She teaches that the key to getting rid of traffic is getting rid of roads. Not everyone buys this theory, but in LA's case, why not try dynamiting the freeways and let's just see if things get better? It's not like they can get any worse.
The ideal plan for Jacobs might be Amsterdam. No cars, no traffic. It's so simple.
A lot of people who remember Jacobs' preference for cities that don't require cars to get around ignore the fact that she didn't necessarily favor central planning and high rises either.
I'm not sure you're ever going to significantly decrease traffic due to induced demand. Probably the best you can do is cap building and force the construction of alternatives and changes in behavior because past some point traffic can't get worse indefinitely.