Cars are driven by humans. The reason it doesn't reduce traffic is the human element. People will turn a 20-lane highway into a parking lot, because there will be increased fuckery as everyone drives like they're the main character.
If one car goes from the left/passing-lane to the exit/off-ramp and it causes several lanes to brake ona four-land highway...what happens on an eight-lane? Again, we have real world examples of it not working.
You want to fix traffic? Make everything you need to live accessible in your community (e.g. markets, retail, schools, work, entertainment, etc.). Cities, especially walkable/bikeable ones, used to be the answer but they built highways that killed that so people could spend hours in traffic to live one place and work another. The best answer at this point is mass transit, not mass serfdom.
We have a city kind of like that in Maryland, and it's considered one of the best places to live in America. It has bike lanes, sidewalks, mass transit, etc combined with multiple parks, entertainment venues, hospitals, schools, residential (apartment/townhouses/single-family homes), etc. all in mixed and split-zoning.
Developer James Rouse founded Columbia in 1967, aiming to create a community that would avoid the inconveniences of then-current subdivision design; eliminate racial, religious and class segregation; and reduce leapfrog and spot zoning development.
I like to based ideas off of evidence, and this is a pretty good practical for how America could work and look.